Great Pyramid of Giza

• 1. Introduction

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  The Great Pyramid of Giza reached 146.6 metres when it was finished. For more than 3,700 years, no human-made structure on Earth stood taller. Today it measures 138.5 metres, because its smooth white limestone skin was stripped away over the centuries. What visitors see now is the rough core underneath.

  It is the largest of the Egyptian pyramids and the oldest of the Seven Wonders of the Ancient World. It is also the only one of those wonders that remains largely intact. This monument at Giza, in Egypt, raises questions that people have asked for thousands of years.

  Who built it, and for whom? Where did millions of stone blocks come from, and who moved them? How old is it, and how can anyone be sure? Visitors from Greece, Rome and the medieval Arab world all offered answers, and many of those answers were wrong. Inside, a maze of passages and chambers is still giving up surprises.

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• 2. A Tomb for Khufu

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  Four jobs fell to every elite tomb in ancient Egypt, and the Great Pyramid carried out all four for the pharaoh Khufu, whom the Greeks called Cheops. It had to shelter his body, display the standing of his family, preserve his place in society, and give people a spot to leave offerings. Khufu ruled in the Fourth Dynasty of the Old Kingdom, and his granite sarcophagus is still inside. An Egyptian text captures the mindset: "Make your grave well furnished and prepare thy place in the west. Look, death counts little for us. Look, life is valued highly by us. The house of the dead (the tomb) is for life."

  Royal decrees in the Old Kingdom wrote down the permitted size of tombs. Only kings and queens could have a pyramid, while smaller mastabas marked everyone else's rank. The king also controlled the layout, the funeral equipment, the materials and the workers. A gigantic pyramid beside a modest mastaba was social inequality set in stone.

  The funerary complex around the pyramid was extensive. Two mortuary temples were joined by a causeway, with one temple near the pyramid and the other near the Nile. Nearby lay tombs for Khufu's family and court, three small pyramids for his wives, an even smaller satellite pyramid, and five buried solar barques. The pyramid temple honoured the Sed festival, which celebrated Khufu's 30th jubilee. Surviving scenes show Khufu, officials and priests performing rituals. The valley temple is largely unexcavated, yet blocks that Amenemhat I later reused show nautical scenes and personified estates, including one called "Khufu is beautiful".

  In 1954 two boat pits were found buried at the south foot of the pyramid, and one held the Khufu ship. Blocks covering the pits bore the cartouche of Djedefre, Khufu's eldest son and successor. As heir, he would presumably have been responsible for the burial. A cult serving Khufu in the temples ran for hundreds of years, which suggests the burial went ahead as planned. The second pit was examined in 1987, and excavation there began in 2010.

  Robbers arrived early. The pyramid was probably looted as far back as the First Intermediate Period, and it may have been reused afterwards. Centuries later, Arab writers described treasure inside. Al-Maqrizi, who lived from 1364 to 1442, reported three shrouded bodies, a sarcophagus filled with gold, and a corpse in golden armour. By his account the corpse carried a sword of inestimable value and a ruby as large as an egg. Yet the chambers themselves carry no inscriptions, because the pyramid predates the custom of inscribing pyramid walls by more than 200 years.

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• 3. Stone and Labor

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  Roughly 2.3 million blocks went into the Great Pyramid. The materials add up to about 5.5 million tonnes of limestone, 8,000 tonnes of granite and 500,000 tonnes of mortar. Most of the limestone was quarried at Giza itself, in the Central Field just south of the pyramid. It is nummulitic limestone, made from fossilised shell creatures whose small discs are still visible in some blocks. Fossilised shark teeth have turned up in the blocks and in other structures on the site.

  The fine white limestone for the casing travelled farther. Boats carried it across the Nile from the Tura quarries, about 10 km south-east of the Giza plateau. The granite came from Aswan, more than 900 km to the south. The largest granite pieces weigh 25 to 80 tonnes and form the ceilings of the King's Chamber and the relieving chambers above it. Workers split rock by hammering grooves into a stone face, pushing in wooden wedges and soaking them. As the wet wood swelled, workable chunks broke away. A now dry offshoot of the Nile brought the blocks close to the building site.

  A set of papyrus rolls found in 2013, called the Diary of Merer, shows this traffic in action. Its author supervised limestone deliveries from Tura to Giza in the 27th year of Khufu's reign. The diary names the pyramid by its original title, Akhet Khufu, dozens of times. Stones were accepted at "the pool of the pyramid Horizon of Khufu" and at "the entrance to the pool of Khufu". Both places were overseen by Ankhhaf, Khufu's half brother and vizier. He owned the largest mastaba in the Giza East Field.

  Graffiti left by workers at Giza reveal how the haulers were organised. Each group, called a za, held 40 men in four sub-units, and each sub-unit had an Overseer of Ten. The ancient Greeks believed slave labour built the pyramid. Discoveries at workers' camps near Giza point instead to thousands of conscript labourers.

  Could one reign supply so many blocks? In 2017 an abandoned Khufu quarry was found, with an almost finished block and the tools used on it. They were hardened arsenic copper chisels, wooden mallets, ropes and stone tools. The stonemason Franck Burgos made replicas and cut a block of about 2.5 tonnes, the average size used in the pyramid. Four workers, each putting in 6 hours a day, needed 4 days. Wetting the stone made the work go six times faster.

  From those results Burgos calculated that about 3,500 quarrymen could produce the 250 blocks a day needed to finish in 27 years. A construction management study from 1999, done with Mark Lehner and other Egyptologists, reached a different kind of estimate. It put the average workforce at about 13,200 people and the peak at roughly 40,000.

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• 4. Design and Skin

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  Flinders Petrie made the first precise measurements of the pyramid in 1880-1882 and published them as The Pyramids and Temples of Gizeh. His numbers still astonish. Many casing and chamber blocks meet with joints averaging only 0.5 mm wide. The four sides of the base have an average error of just 58 mm in length, and the corners are square to a mean error of 12 seconds of arc.

  Before building began, the builders cut the natural hillock into steps and levelled a strip around its edge flat to within 21 mm. Lehner suggests that holes cut in the bedrock along the base held wooden posts for alignment. Edwards proposed that water was used to even out the base, though it is unclear how workable that would be. Hemiunu, Khufu's vizier, is believed by some to have been the architect.

  Behind the fine outer work, the core blocks were only roughly shaped, with rubble packed into the larger gaps. Petrie measured the lowest course at 148 cm high, while courses near the summit barely exceed 50 cm.

  The design called for a height of 280 royal cubits and a base of 440 royal cubits on each side. Egyptians described a slope by its seked, the run for each cubit of rise. The Great Pyramid's slope is a ratio of 14 up to 11, which gives an angle of 51°50'40".

  Some Egyptologists think this slope was chosen because the perimeter over the height, 1760 over 280 cubits, equals 2π with an error below 0.05 percent. Verner wrote: "We can conclude that although the ancient Egyptians could not precisely define the value of π, in practice they used it". Petrie judged the relations of areas and circular ratio to be "so systematic that we should grant that they were in the builder's design". Others argue that the Egyptians had no concept of pi and that the seked choice alone explains the slope.

  The sides of the base face the true cardinal directions, not magnetic ones, with an average deviation of 3 minutes and 38 seconds of arc, about a tenth of a degree. Several methods have been proposed. In the solar gnomon method, the shadow of a vertical rod is tracked through a day to find an east-west line. An experiment produced lines that were on average 2 minutes 9 seconds off. A pinhole improved that to 19 arc seconds, while an angled block did worse at 3 minutes 47 seconds.

  The pole star method tracks Thuban, the Old Kingdom's polar star, with a movable sight and a plumb line. Thuban sat about two degrees from the celestial pole, so true north lies halfway between its eastern and western extremes. A third method uses the stars Mizar and Kochab, which line up vertically near true north around 2500 BC. They drift east together over time, and that drift could explain why the pyramids are slightly misaligned.

  John Romer suggests the planners laid out the design on the ground at a 1-to-1 scale, as in earlier and later projects. He argues that such a working diagram would give unmatched precision. He also proposes a "super saw" to cut the basalt blocks of the pyramid temple. It would have had a blade about 15 ft long, perhaps with copper teeth, weighing up to 140 kg. At least a dozen men would have worked it with vegetable oil and cutting sand, emery or pounded quartz.

  When finished, the whole pyramid wore a coat of white limestone, set in horizontal layers and joined with mortar. The outer faces were cut to the slope and smoothed. Unfinished casing blocks at the pyramids of Menkaure and Henutsen show that the faces were dressed only after the stones were laid. Of the 203 courses that remain, the tallest are near the bottom, while those near the top are a little over one royal cubit high, with stones around 500 kg. Precisely dressed backing stones supported the casing, and they now form the visible surface.

  In 1356, according to tradition, the Bahri Sultan An-Nasir Nasir-ad-Din al-Hasan had casing stones carted off for use in nearby Cairo. Earthquakes in northern Egypt had already brought many outer stones down. Later explorers reported huge piles of rubble at the foot of the pyramids, which excavations cleared. A few casing stones from the lowest course remain in place on each side. The best preserved are on the north, below the entrances, uncovered by Vyse in 1837.

  In 1880 Petrie noted that each face was "very distinctly hollowed", with a groove down the middle. Under certain lighting, and with image enhancement, the faces can look split. That fed speculation that the builders made the pyramid eight-sided on purpose. Laser scanning and photogrammetric surveys showed instead that the concavities come from casing removal, which damaged the blocks beneath. A theory that the casing was cast-in-place concrete has also been ruled out by archaeological evidence and petrographic analysis.

  A capstone called the pyramidion once crowned the pyramid. Popular culture often makes it solid gold, gilded or electrum, while scholars propose limestone, granite or basalt. Every known Fourth Dynasty pyramidion is white limestone and ungilded, including those of the Red Pyramid and the satellite pyramid of Khufu. Gilded capstones appear only from the Fifth Dynasty, when a scene on the causeway of Sahure mentions the "white gold pyramidion of the pyramid Sahure's Soul Shines". The Great Pyramid's own capstone was gone by classical antiquity, and about 1000 tonnes of material are missing from the top.

  In 1874 the Scottish astronomer David Gill, returning from observing a rare Venus transit, was invited to survey Egypt. He began with the Great Pyramid and set up a mast on the summit, and his measurements were accurate to within 1 mm. In 2019 a man who evaded security climbed the pyramid and damaged the mast. Because the mast was periodically replaced and counted as a modern object, he did not break Egypt's strict antiquities laws.

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• 5. Names and Dates

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  In 1837, tunnelling reached four relieving chambers above the King's Chamber that had been inaccessible until then. Their blocks were covered in hieroglyphs painted in red. They were marks left by the work gangs, and they included the pharaoh's name. One reads, "The gang, The white crown of Khnum-Khufu is powerful". Khufu's names are spelled out on the walls more than a dozen times. Goyon later found another such mark on an exterior block of the 4th layer. Similar inscriptions appear at other Khufu sites, including the alabaster quarry at Hatnub and the harbour at Wadi al-Jarf.

  Excavations throughout the 20th century uncovered the cemeteries beside the pyramid. Family members and high officials of Khufu lay in the East Field and the West Field. Burials there include his wives, children and grandchildren, Hemiunu, Ankhaf and the funerary cache of Hetepheres I, Khufu's mother. Hassan explained the practice: "From the early dynastic times, it was always the custom for the relatives, friends and courtiers to be buried in the vicinity of the king they had served during life. This was quite in accordance with the Egyptian idea of the Hereafter." The cemeteries kept growing until the 6th dynasty. Seal impressions there run from Khufu, the earliest pharaoh named, to Pepi II, the latest.

  The tombs mention Khufu again and again. An inscription of Mersyankh III states that "Her mother is the daughter of the King of Upper and Lower Egypt Khufu." Nykahap held the title "priest of Khufu who presides over the pyramid Akhet-Khufu". Several tomb owners wore the king's name inside their own, among them Chufudjedef, Chufuseneb and Merichufu.

  In 1936 Hassan uncovered a stela of Amenhotep II near the Great Sphinx. It describes the young prince stopping at the Sanctuary of Hor-em-akhet and spending time "looking at the beauty of the Sanctuary of Khufu and Khafra the revered." The text shows that in the New Kingdom the two larger pyramids were still credited to Khufu and Khafre.

  The Great Pyramid is about 4,600 years old, and two main approaches support that figure. One works indirectly, through Khufu's place in Egyptian chronology. The other dates organic material found in the pyramid and in its mortar. The older method adds up reign lengths backwards from known points, helped by genealogy and astronomical observations. Most recent estimates place Khufu and his pyramid between 2700 and 2500 BC.

  Earlier scholars were far less certain. Herodotus, around 450 BC, placed Khufu after the Ramesside period. Manetho, about 200 years later, listed Khufu in the 4th dynasty, but sound changes had turned "Cheops" into "Souphis". In 1646 Greaves could not recognise Khufu on that list, trusted Herodotus, and arrived at 1266 BC. By 1867 Mariette proposed 4235 BC. Later finds, including the King Lists of Turin, Abydos and Karnak, filled gaps in Manetho. The names in the relieving chambers showed that Cheops and Souphis were one king. Even so, estimates ranged from about 4000 to 2000 BC, shaped by method and by notions such as the biblical flood. In the 20th century most settled within 250 years of one another.

  Mortar offered a second route. Ashes from fires were mixed into it, and that organic material could be radiocarbon dated. Researchers took a total of 46 samples in 1984 and 1995, choosing only those clearly part of the original structure. The results calibrated to 2871-2604 BC. The "old wood problem" is thought to explain most of an offset of 100-300 years, since the test reveals the age of the material, not when it was last used. A reanalysis using the younger samples gave a completion date between 2620 and 2484 BC. Ramsey and colleagues later included over 200 radiocarbon samples in their model, which gave 2613-2577 BC for the start of Khufu's reign.

  In 1872 Waynman Dixon opened the lower pair of air shafts, which had been closed at both ends, by chiselling holes into the walls of the Queen's Chamber. Inside one lay a cedar plank, which passed to his friend James Grant. After inheritance it was donated to the Museum of Aberdeen in 1946. There it broke into pieces and was filed incorrectly. Lost in a vast collection, it was rediscovered only in 2020. Radiocarbon dating gave 3341-3094 BC, over 500 years older than Khufu's chronological age. Abeer Eladany suggests the wood came from the centre of a long-lived tree or was recycled for many years before it was placed in the shaft.

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• 6. Classical Witnesses

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  Herodotus, writing in the 5th century BC, is among the first major authors to describe the Great Pyramid. His account in the second book of The Histories came more than 2000 years after construction. He relied on low-ranking officials and priests, local Egyptians, Greek immigrants and his own interpreters. The result mixes sound description with errors and fantastical legends, and many later confusions trace back to him.

  Herodotus called Khufu a tyrant, which fits his view that such buildings can only come from cruel exploitation. He held that gangs of 100,000 labourers worked in three-month shifts for 20 years. The first ten years, he said, went to a wide causeway nearly 1 km long, 20 yards wide and 16 yards high, made of polished stone carved with figures. Underground chambers on the hill were meant for Khufu's burial and were fed by a channel from the Nile. Hawass reads his later remark about the Nile flowing to an island where Khufu lay as a reference to the Osiris Shaft, near the causeway of Khafre.

  Herodotus also described an inscription on the outside of the pyramid. His translators told him it recorded the radishes, garlic and onions the workers ate. It may really have been a note about restoration work by Khaemweset, son of Rameses II. His companions and interpreters apparently could not read hieroglyphs, or they deliberately gave him false information.

  Between 60 and 56 BC, Diodorus Siculus visited Egypt and devoted the first book of his Bibliotheca historica to its land, history and monuments. He distanced himself from Herodotus, accusing him of telling marvellous tales and myths. He probably drew on the lost work of Hecataeus of Abdera. Diodorus reported that neither Chemmis, his name for Khufu, nor Cephren lay in their pyramids. They were buried in secret places, he wrote, for fear that the people supposedly forced to build the monuments would take revenge on the bodies. That claim strengthened the link between pyramid building and slavery.

  Diodorus said ramps raised the stones, since no lifting tools existed yet, and that the ramps were removed once the work was done. He estimated 360,000 workers and a construction time of 20 years. Like Herodotus, he reported an inscription on the pyramid. His version listed the price of vegetables and purgatives for the workmen, which came to over sixteen hundred talents.

  Around 25 BC, shortly after Rome annexed Egypt, the Greek geographer Strabo visited. He wrote in his Geographica that the pyramids were burial places for kings, without saying which king. He added: "At a moderate height in one of the sides is a stone, which may be taken out; when that is removed, there is an oblique passage to the tomb." The sentence suggests the pyramid could still be entered then, and it has generated much speculation.

  In the first century AD, Pliny the Elder offered two motives for the building: "to prevent the lower classes from remaining unoccupied", or to keep the pharaoh's riches from rivals and successors. He did not name the king, noting that "accident has consigned to oblivion the names of those who erected such stupendous memorials of their vanity". On raising the stones, he offered two ideas. One was vast mounds of nitre and salt, melted away with water diverted from the river. The other was "bridges" whose bricks were later reused for houses. Pliny also reported a well 86 royal cubits deep, thought to connect with the river, and a method credited to Thales of Miletus for finding the pyramid's height from its shadow.

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• 7. Granaries and Legends

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  The pilgrim Egeria visited Egypt between 381 and 384 AD and left a note about the many pyramids between Memphis and Babylonia, meaning Old Cairo. In her telling, Joseph had built them to store corn. About ten years later, an anonymous travelogue by seven monks from Jerusalem said they "saw Joseph's granaries, where he stored grain in biblical times". Julius Honorius, writing his Cosmographia around 376 AD, called the pyramids the "granaries of Joseph" (horrea Ioseph). That showed the idea spreading beyond pilgrims' diaries. In 530 AD, Stephanos of Byzantium tied the word "pyramid" to the Greek pyros, meaning wheat.

  In 642 the Rashidun Caliphate conquered Egypt, ending several centuries of Romano-Byzantine rule. A Coptic legend then grew that the antediluvian king Surid Ibn Salhouk had built the Great Pyramid. According to one version, three hundred years before the Great Flood, Surid dreamed of the end of the world. He ordered pyramids built to hold all the knowledge of Egypt and carry it into the future. Al-Masudi, who lived from 896 to 956, gave the most notable account in his Akbar al-zaman. He set it beside tales of a man who fell for three hours down the pyramid's well and of an expedition that found bizarre things in the inner chambers.

  The same book reports that the caliph al-Ma'mun, on entering, found an emerald jar holding a thousand coins, each weighing four ounces. Together they just covered the cost of opening the pyramid. Some speculate the story is true, and that the caliph planted the coins to calm workers frustrated at finding no treasure.

  In 987 AD, the Arab bibliographer Ibn al-Nadim told in al-Fihrist of a man who journeyed into the main chamber of a pyramid. Bayard Dodge argues it was the Great Pyramid. The man saw a statue of a man holding a tablet and a woman holding a mirror, and between them a "stone vessel with a gold cover". Inside lay something like pitch, and beneath it a gold receptacle filled with "fresh blood", which quickly dried up. The same author claims bodies of a man and a woman were found in the "best possible state of preservation".

  Al-Kaisi, in his Tohfat Alalbab, retold the caliph's entry with an extra discovery: "an image of a man in green stone". When opened, it revealed a body in jewel-encrusted gold armour. Al-Kaisi claims he saw the case it came from at the king's palace in Cairo. Another treasure hunt, recorded during the vizierate of al-Afdal Shahanshah, which ran from 1094 to 1121, was abandoned after a member of the party was lost in the passages.

  Some medieval voices were sober. In the ninth century, Dionysius I Telmaharoyo rejected the granary idea and said the pyramids were tombs, and solid. The Arab polymath Abd al-Latif al-Baghdadi, who lived from 1163 to 1231, studied the pyramid with great care in his Account of Egypt. He measured it, praised the pyramids as works of engineering genius, and judged them tombs. He guessed the Great Pyramid held the burial of Agathodaimon or Hermes. He even wondered whether it predated the Flood described in Genesis, and briefly entertained a pre-Adamic origin. By the Late Middle Ages the pyramid had a reputation as a haunted place, and others stayed out because bats lived inside.

  In 1435 Cyriacus of Ancona sailed up the Nile to the Giza plateau. He is considered the founding father of modern classical archaeology, because he paired the reading of ancient texts with the hunt for statues, inscriptions and monuments. At Giza he compared what he saw with the second book of Herodotus's Histories. That comparison let him recover the true nature of the Great Pyramid and refute its identification as one of Joseph's granaries. He left drawings and an account in his Commentarii. News of his findings travelled first through Italian humanist circles and then reached scholars across Europe.

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• 8. Inside the Pyramid

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  The original entrance sits on the north side, 15 royal cubits east of the centreline. Before the casing was stripped, visitors entered through a hole in the 19th layer of masonry, about 17 m above the base. That layer is 96 cm high, matching the size of the Descending Passage behind it. Rows of double chevron blocks divert weight away from the opening. Near it is a large square of hieroglyphs carved in honour of Frederick William IV by Karl Richard Lepsius's Prussian expedition in 1842.

  Tourists today enter through the Robbers' Tunnel, forced through the 6th and 7th layers about 7 m above the base. It runs straight for 27 m, then turns sharply left to meet the blocking stones of the Ascending Passage. Tradition credits workmen of Caliph al-Ma'mun, who around 820 AD supposedly used a battering ram. The noise of a dislodged ceiling stone falling told them to turn left. Unable to move the plug, they dug upward beside it through softer limestone.

  Many scholars call that story apocryphal, with Antoine de Sacy perhaps the first. They argue that robbers cut the tunnel soon after the pyramid was sealed, and that it was resealed, probably in the Ramesside Restoration. The caliph's expedition then cleared the plug. Support comes from the patriarch Dionysius I Telmaharoyo, who described a breach in the north face reaching 33 m into the structure before it hit a dead end.

  The Descending Passage drops from the original entrance at an angle of 26°26'46", a ratio of 1 to 2. After 28 m it passes the lower end of the Ascending Passage, marked by a square hole in the ceiling blocked with granite. It continues another 72 m through bedrock toward the Subterranean Chamber. Around 1902, Covington fitted a padlocked iron grill-door here. Lazy guides had been blocking this stretch with rubble to avoid leading visitors down and back up.

  The Subterranean Chamber lies about 27 m below base level and is the only chamber cut into the bedrock. It measures roughly 16 by 27 royal cubits and stands about 4 m high. Its western half is unfinished, with trenches left by the quarrymen. Herodotus and later authors seem to have known of it, yet it was forgotten in the Middle Ages until Giovanni Caviglia cleared the rubble in 1817. A Greek or Roman character found on the ceiling of a blind corridor by candlelight suggests it was accessible in classical times.

  In 1837 Vyse had the pit shaft sunk to a depth of 50 ft, hoping to find the water-encircled chamber that Herodotus mentioned. Perring and his workers spent one and a half years cutting down to the then water level of the Nile and found nothing. Ludwig Borchardt suggested that this room was first planned as Khufu's burial place and then abandoned for a chamber higher up.

  The Ascending Passage is 75 royal cubits long and rises at 26°6'. Its lower end is plugged by three granite stones, 1.57 m, 1.67 m and 1 m long, slid down from the Grand Gallery to seal it. A winding Well Shaft links the lower end of the Grand Gallery to the bottom of the Descending Passage, about 50 m below. It is commonly explained as ventilation for the Subterranean Chamber and an escape route for the workers who slid the plugs into place. Along it lies the Grotto, a natural limestone cave probably filled with sand and gravel before construction and later hollowed out by looters.

  The Grand Gallery rises 21 m, from the 23rd to the 48th course of stones, and is 46.68 m long and 8.6 m high. Its polished limestone walls are corbelled inward in seven steps, narrowing from 4 royal cubits at the base to 2 at the top. The roof slabs are laid at a slightly steeper angle than the floor, each fitting into a slot like the teeth of a ratchet. That way each slab rests against the wall instead of the block beneath, which prevents pressure from building up. The floor has 56 slots, 28 on each side, and each wall has 25 niches. Their purpose is unknown. Jean-Pierre Houdin theorised that they held a timber frame, used with a trolley to pull heavy granite blocks upward.

  The Queen's Chamber lies exactly halfway between the north and south faces. It measures 10 royal cubits north-south and 11 east-west, with a pointed roof that reaches 12 cubits. A niche at the east end is 9 cubits high, and treasure hunters have deepened it. Shafts in the north and south walls connect neither to the chamber nor to the outer faces, and their purpose is unknown. Dixon found a ball of diorite and a bronze hook in one of them, and both objects are now in the British Museum.

  In 1993 the German engineer Rudolf Gantenbrink sent a crawler robot he designed, Upuaut 2, up one shaft. After a climb of 65 m, he found a limestone "door" with two eroded copper "handles". In September 2002 a robot built by the National Geographic Society drilled a small hole in the southern door and found another slab behind it. The twisting northern shaft was also blocked by a slab. In 2011 the Djedi Project pushed a fibre-optic "micro snake camera" through the hole and saw hieroglyphic characters in red paint. Luca Miatello stated that they read "121", the length of the shaft in cubits. The team judged the copper handles decorative and found the back of the door polished, which suggests the door had a more specific purpose than blocking debris.

  The Antechamber, cased almost entirely in granite, was the last defence against intruders. It held three portcullis stones, each about 1 royal cubit thick, lowered by ropes through four holes at the top of each block. It had a design flaw, because the space above the stones could be reached. Looters punched a hole through the ceiling of the tunnel behind and bypassed all but the last stone. All three stones were later broken and removed. Fragments turn up in the Pit Shaft, the Original Entrance, the Grotto and the recess before the Subterranean Chamber.

  The King's Chamber is faced entirely with granite and measures 20 royal cubits east-west by 10 north-south. Its flat ceiling, 5.8 m above the floor, is formed by nine slabs weighing about 400 tons in total. All of them have cracked as the chamber settled. The one surviving object is a sarcophagus carved from a single block of granite, found broken open in the Early Middle Ages with its contents gone. Its internal dimensions are roughly 198 cm by 68 cm. Tool marks match copper saws and tubular hand-drills.

  Hidden spaces are still turning up. In 2016 the ScanPyramids team used muography to detect a cavity behind the entrance chevrons, confirmed in 2019 as a corridor at least 5 m long. In February 2023 an endoscopic camera showed a horizontal tunnel 9 m long, roofed with large chevrons.

  In 2017 ScanPyramids scientists found a much larger cavity above the Grand Gallery, which they called the ScanPyramids Big Void. A team led by Professor Morishima Kunihiro at Nagoya University used special nuclear emulsion detectors. The void is at least 30 m long, with a cross-section similar to that of the Grand Gallery. Three technologies confirmed it independently: nuclear emulsion films, scintillator hodoscopes and gas detectors. Zahi Hawass speculates it may be a gap used during construction. The Japanese team says it is completely different from known construction spaces. Teams from Kyushu University, Tohoku University, the University of Tokyo and the Chiba Institute of Technology planned a rescan with a newly developed detector in 2020, but the COVID-19 pandemic delayed their work.

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