Short answers, pulled from the story.
Human settlement at Erbil dates back to the 5th millennium BC, placing it among the oldest continuously inhabited cities on earth. The earliest evidence of occupation on the Citadel mound reaches to the fifth millennium BC or possibly earlier, and the city appears in written records from the Ur III period of ancient Sumer.
The Citadel of Erbil is an ancient occupied mound rising 25-32 metres above the surrounding plain, with buildings spread over an oval area of 430 by 340 metres. It was inscribed on the UNESCO World Heritage List on the 21st of June 2014.
The Mongols first attacked Erbil in 1237, plundering the lower town. After the fall of Baghdad in 1258, the citadel resisted until a six-month siege forced its surrender. On the 1st of July 1310, a later assault by Ilkhanate troops and Kurdish tribesmen ended with the massacre of the citadel's defenders.
The Battle of Gaugamela, in which Alexander the Great defeated Darius III of Persia in 331 BC, took place approximately 100 km west of Erbil according to Urbano Monti's world map. After the battle, Darius fled to Erbil, and the confrontation is sometimes called the Battle of Arbela, the ancient name for the city.
The Assyrian Church of the East moved its global seat from Chicago to Erbil in 2015. Erbil had previously served as a centre of eastern Syriac Christianity for over a thousand years, with Pkidha recorded as its first bishop around 104 AD.
Parallel bomb attacks targeting Eid celebrations in February 2004 killed 117 people, with Ansar al-Sunnah claiming responsibility. A suicide bombing in May 2005 outside a police recruiting centre killed 60 civilians and injured 150 more. Further missile attacks hit the city in February 2021 and March 2022.