Disguising itself as a flat, 79B Aickman Road was a timeship that belonged to the Silence, (TV: Day of the Moon) described by the Doctor as "someone's attempt to build a TARDIS" when he first saw it in Colchester in 2010. (TV: The Lodger)
From outside, 79B was somewhat like an inverted, curved pyramid, with four legs/landing struts. It had a perception filter to blend in with its surroundings and convince anyone who looked upon it that it had always been there. When it took on the appearance of the non-existent upper floor of 79B Aickman Road, even Craig Owens, who lived in the house, accepted the reality of a second storey.
The ship drew power from its pilots, who steered the ship with their thoughts. Humans were incompatible; the energy-drawing process invariably resulted in the candidate's death. Time Lords were too much for the system and would overload it, enough to blow up the solar system.
The ship had a holographic autopilot which activated when damaged. The autopilot searched for people to power the ship, using the building's intercom to communicate with people outside and changing its appearance to lure them in. All of the holograms seemed to lure the victims by saying that they needed help. (TV: The Lodger)
When the Eleventh Doctor defeated the Silents in 1969, he, River Song, and Rory Williams rescued Amy Pond from their base which resembled 79B Aickman Road, already encountered by the Doctor. River subsequently killed every Silent present. (TV: Day of the Moon)
The base eventually proved to be a timeship, leaving 1969 and crash-landing on Earth some time before 2010. The ship hid itself by pretending to be 79B, the upper story of 79 Aickman Road over a flat occupied by Craig Owens.
The ship's autopilot attempted to relaunch the ship using humans as pilots, specifically selecting humans who wanted to escape or explore. However, the mind of a human was too weak to launch the ship and the people selected by the autopilot were killed. This created a pattern of decay on the ceiling below, much like rot in appearance. The autopilot's attempt to launch the ship with humans also caused a time loop to form briefly, almost resulting in the TARDIS and Amy Pond being thrown into the Time Vortex.
The Auto Pilot attempted to use the Eleventh Doctor's mind to launch the ship, but the Doctor claimed that his mind would be too much for the system to handle. Craig Owens interfaced with the ship, which shut down because he didn't want to escape or explore; he wanted to stay right where he was. The ship vanished when the emergency shutdown was activated by Craig. (TV: The Lodger)