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)

It was revealed that the Drum, before it was flooded was the location of the Fisher King's plan to be rescued and take over. The Doctor detonated a power cell and broke the dam, flooding the Drum and killing the Fisher King. In the present, the Doctor retraps the ghosts in the Faraday cage and contacts UNIT who he states will cut the cage out of the base and launch it into space. Once far enough from the Earth's magnetic field, the ghosts will dissipate. (TV: Before the Flood)