Aplan Mortarium

The Aplan Mortaria, also known as mazes of the dead, were a type of structure built by the Aplans on their home planet Alfava Metraxis.

They were large subterranean labyrinths with tombs in the walls, adorned with statues of the dead. The Mazes had six levels, to represent the ascent of the soul. During the 47th century, these mazes apparently became infested with Weeping Angels, leading to the downfall of their civilisation. (DW: The Time of Angels)