The Black Archive was a secret vault maintained by UNIT.
It was relocated to the Tower of London.
It functioned as a depository of everything that shouldn't exist on Earth but did anyway, and required a UNIT level one clearance to gain entrance. (TV: Enemy of the Bane) The staff had their memories erased after every shift. (TV: The Day of the Doctor) In the event of alien invasion the contents of the Black Archive were deemed so dangerous that the nuclear warhead situated 20 feet beneath the archive was to be detonated in order to prevent the invading species from gaining access to the technology contained within the archive. (TV: The Day of the Doctor)
At some point, UNIT started keeping a particular eye on the Doctor's companions by taking them to the archive while they were separated from the Doctor; the companions' memories of the visit were subsequently erased, but UNIT kept a wall of photographs of the companions after confirming that they could be trusted (TV: The Day of the Doctor).
On 4 June 1972, UNIT bought the Tunguska Scroll from a private collector and placed it in the Black Archive. In 2009, Brigadier Lethbridge-Stewart smuggled Sarah Jane Smith into the archives to steal the scroll. (TV: Enemy of the Bane) During the same year, the Tenth Doctor sent Martha Jones there to fetch information on the Krynoid virus in the hopes that it might hold a key to stopping the Enochian invasion in Greenwich Park. (COMIC: Don't Step on the Grass)
In the 21st century, a vortex manipulator had been donated to the archive by Captain Jack Harkness. A Zygon impersonating Kate Stewart took Clara there to retrieve it. Clara used the manipulator to escape the Zygon, and travelled to 1562 to rescue three incarnations of the Doctor. Having free reign of the base, the Zygons believed that they could overrun the Earth easily with the amount of alien technology now in their possession. The genuine Kate Stewart then turned up however, and activated the nuclear armed self-destruction mechanism located under the base. The Zygon who was imitating Kate was able to shut off the device, which was keyed to respond to Kate's voice, but the real Kate could likewise countermand it. This resulted in a deadlock between the two. Eventually the Eleventh, the Tenth, and the War Doctor turned up to stop her. They activated the memory erasing equipment in the ceiling, meaning the two sets of people forgot whether they were human or Zygon, and stopped the self-destruction mechanism. This saved themselves and the whole of London, also resulting in peace talks between the humans and the Zygons. (TV: The Day of the Doctor)
- Tunguska Scroll, stolen by Sarah Jane Smith in 2009 (TV: Enemy of the Bane)
- Magna-Clamps, (TV: The Day of the Doctor) identical to those recovered by Torchwood One from a crashed spaceship in Mount Snowdon, used by the Tenth Doctor and Rose Tyler to end the Battle of Canary Wharf. (TV: Army of Ghosts/Doomsday)
- The head of a Cybus/Cyber Legion Cyberman.
- The head of a Supreme Dalek (TV: The Day of the Doctor) identical to the one who led the New Dalek Empire. (TV: The Stolen Earth/Journey's End)
- A pair of red heeled shoes (TV: The Day of the Doctor) identical to the ones River Song wore on the Byzantium. (TV: The Time of Angels)
- Time Agent vortex manipulator donated by Jack Harkness circa 2013 (TV: The Day of the Doctor)
- Space-time telegraph originally given to Alistair Gordon Lethbridge-Stewart by the Doctor, allowing direct communication to the TARDIS (TV: The Day of the Doctor).
- A board containing photographs of all of the Doctor's past companions (Including a meeting between Mike Yates and Sara Kingdom) (TV: The Day of the Doctor)
- A Dalek tommy gun (TV: The Day of the Doctor) identical to the ones used by the Cult of Skaro on 1930 (TV: Evolution of the Daleks)
- Chair from the Naismith Mansion, which The Master tied the Tenth Doctor to. (TV: The End of Time)
- Half part of a Silent.
- A TARDIS coral.
- Facemask of one of the Clockwork Droids (TV: The Girl in the Fireplace)
- Amy Pond's pinwheel (TV: The Eleventh Hour)
- The sonic probe used by an older version of Amy (TV: The Girl Who Waited)
- A Sontaran blaster
Behind the scenes
- In an interview after the broadcast of Day of the Doctor, Steven Moffat revealed that the Black Archive was at one point also to house two movie posters for Dr. Who and the Daleks and Daleks' Invasion Earth 2150 A.D., which Clara was to have been seen examining, establishing the Peter Cushing films as existing within the Whoniverse. Rights fees prevented this from happening.