A catacomb was an underground cemetery made up of galleries.
The showdown for the first piece of the Key to Time took place in the catacombs of Ribos. Some of the natives of the planet feared the place as the home of the Ice Gods. (TV: The Ribos Operation)
On Alfava Metraxis, the team led by Octavian had to cross a network of catacombs (which he called "Maze of the Dead") to reach the Weeping Angel they were intended to neutralise. (TV: The Time of Angels)
In the underground of the battlefield graveyard on Trenzalore, Clara Oswald confessed she hated catacombs. (TV: The Name of the Doctor)