Palace of the Old Ones

The Palace of the Old Ones was a structure built by the Old Ones on Ashkellia. It was the control centre for the particle accelerator they used to access the higher dimensions. It was self-maintaining and self-regenerating, with architecture that remodelled itself on the occupants' wishes. When the Fourth Doctor and Romana arrived there, it had existed for over a million years. (PROSE: Tomb of Valdemar)