From PathfinderWiki

The impressive palace of Bandeshar is located in the Nexian capital of Quantium. It is situated in the middle of the city's lake.1

It was once the palace of the archmage Nex, and today is the meeting place of the ruling Council of Three and Nine. The palace is an architectural marvel, and was designed by Elder Architect Oblosk, an ancient pech who still lives and holds the title Castellan of Bandeshar. He is believed to know most of the palace's architectural secrets.2 Its lower dungeons contain an entrance to the Refuge of Nex, believed to be the location of the long-vanished archmage.3 The Bandeshar is also said to hold three of the remaining cubes of force created by Nex himself: those associated with the schools of evocation, necromancy, and transmutation.4