The Drum

 was an underwater mining facility in Caithness, Scotland in 2119.

Once it used to be a military training site, but when a dam broke, the site was flooded and destroyed.

It had a canteen, a control room, an airlock to allow them to venture outside and a Faraday cage.

Since the facility was underwater and there was no natural light, the facility was programmed to go into day and night mode to alert people on the base what time of day it was.

The base was visited by the Twelfth Doctor and Clara Oswald who arrived by orders from the TARDIS, when the base was haunted by ghosts. The ghosts couldn't manifest during the day shift but could hack into the Drum's controls and switch the shift. The crew used the Faraday cage to hide and later trap the ghosts as the ghosts couldn't get through the cage doors.

Crewmembers included Cass, Tim Lunn, Mason Bennett, Alice O'Donnell, Richard Pritchard and Jonathan Moran. (TV: Under the Lake)