Aplan Mortarium
An Aplan Mortarium, also known as a "maze of the dead", was a kind of crypt built by the Aplans on their home planet Alfava Metraxis.
It was a large temple with subterranean labyrinths, with tombs in the walls and adorned with statues of the dead. The Maze had six levels, to represent the ascent of the soul. During the 47th century, these mazes became infested with Weeping Angels, leading to the downfall of the Aplan civilisation. (DW: The Time of Angels)
Large, dark, spacious and full of statues, the Mortaria is the perfect home and hiding place for creatures like the Weeping Angels. The darkness makes hunting a lot easier and the Angels have a less likely chance of locking themselves in stone form due to the darkness. In the 51st century the Doctor visits the Maze of the Dead with Father Octavian and River Song. The Doctor realises that the Aplans, a two-headed species, would not have built single-headed statues; which means that every single "statue" inside the maze was in fact a dying Weeping Angel.
The Doctor hypothesizes that the Byzantium did not crash accidentally; rather it was sabotaged near Alfava Metraxis by a lone Weeping Angel in order to free its fellows, which thanks to his efforts, were slowly starting to come back to life.
