The Forge Alpha Facility was a twenty-five level underground base used by Department C4. It was destroyed in 2008 by a clone of the Sixth Doctor. (AUDIO: Project: Lazarus, PROSE: Project: Valhalla) In the 22nd century, it was remembered as the Forge's primary facility. (PROSE: Twilight's End)
The main entrance to the facility was located in a bowl in the terrain near Lynch Tor. It was marked on maps as a military training camp. Although this kept out most civilians, hikers occasionally accidentally wandered near the Alpha Facility's entrance. (PROSE: Project: Valhalla, AUDIO: Project: Lazarus)
In the 1910s, at least a portion of it had the outward appearance of a metal shack. It was surrounded by barbed wire. The building was usually very cold and drafts of wind could often be heard going through the building's long corridors. Each night, ice formed on the windows of Dr William Abberton's laboratory. (AUDIO: Project: Twilight)
During World War I, the building was used for experiments for Project: Twilight. At least 57 test subjects were taken to the facility and injected with the Twilight Virus. On 4 October 1915, these test subjects escaped from the facility, killing 20 of the facility staff. (AUDIO: Project: Twilight, PROSE: Project: Valhalla)
After the war, the Forge began expanding their facility downwards. A fireplace in the lobby of the old asylum was turned into the entrance for a lift that connected these underground levels to the surface.
By 2001, the facility had 25 levels. The first 12 floors contained vehicle bays, laboratories, barracks, a gym, a firing range, and several storage areas. The thirteenth floor contained Charles Crichton's office and the mess hall. Floors 14 to 25 mostly contained research labs which were off-limits to low-ranking Forge personnel.
A network of lifts and ladders connected the facility with the outside world. The main lift exited into the crumbling remains of the asylum. A helicopter landing pad was located nearby. (PROSE: Project: Valhalla)