A moratorium is in effect on adding information from Fire and Blood until December 20th.
After defeating a dozen castles in the vicinity of Blackwater Bay, Aegon I Targaryen commanded the defeated lords to attend him at the Aegonfort atop what would become known as Aegon's High Hill. There, the lords laid their swords at the conqueror's feet, and he confirmed them in their lands and titles.
Over the next few decades, the Aegonfort grew larger and came to spread halfway down Aegon's High Hill. It was a sloppy confusion of wood, earth, and brick which had long ago outgrown the old log palisades that were its only walls. In 35 AC the elderly King Aegon I came to the realization that the ramshackle pile of wood and earth that his seat consisted of was entirely unsuited to be the seat of power for a king. Aegon moved his family back to Dragonstone, the ancient seat of House Targaryen, and ordered the Aegonfort razed to the ground. Construction of a castle began, which would later become known as the Red Keep.