Short answers, pulled from the story.
The world's oldest known horse stables were built in the ancient Egyptian city of Pi-Ramesses, established by the pharaoh Ramesses II between 1304 and 1213 BC. These structures covered approximately 182,986 square feet and housed about 480 horses with deliberately sloped floors for drainage.
These ancient facilities were critical military assets designed to maintain a powerful cavalry force that could project power across the known world. The pharaoh maintained a complex logistical system to feed and care for hundreds of horses, making the stable a central pillar of ancient Egyptian statecraft and warfare.
Free-standing stables began to be built from the 16th century in historical England. While many have been converted or repurposed, the few surviving examples from the mid-19th century or earlier offer a rare glimpse into the original interiors.
Stables in Great Britain traditionally featured a hayloft on the upper floor and a pitching door at the front with doors and windows symmetrically arranged. Floors were cobbled or later bricked and featured drainage channels to manage waste, while an outside stone stairway constructed against the side of the building was common for reaching the upper level.
The word stable has evolved to become a metonym for the collection of horses that the building contains and metaphorically to refer to a group of people trained, coached, supervised, or managed by the same person or organization. Art galleries refer to the artists they represent as their stable of artists, and car enthusiast magazines speak of collectible cars in this way.
Modern stables include American-style barns with a door at each end and individual stalls inside, as well as free-standing stables with top and bottom-opening doors. A building with tie stalls is also known as a stanchion or stall barn, where animals are tethered by the head or neck to their stall.