Maegor's Holdfast is a location in the second season. It is a stout tower in the centre of the Red Keep in King's Landing. It was built by King Maegor Targaryen. It serves as a redoubt when the city is attacked in the Battle of the Blackwater.
Queen Regent Cersei Lannister hosts the women of the court there when the city is attacked by King Stannis Baratheon. They take refuge in a sparse stone walled room fitted with bunk beds. Cersei has a larger double bed on a dais.