Bubble universe

The bubble universe was a tiny universe which was home to the sentient planetoid known as House. House lured Time Lords from the main universe through the bubble universe rift so it could consume their TARDISes. The Eleventh Doctor and many other Time Lords were drawn to the bubble universe by distress hypercubes, presumably those of House's previous victims. Notably, the bubble universe also included a junkyard filled with dead TARDIS parts left behind by Time Lords lured into House's trap. The bubble universe was destroyed soon after House left it inside of the Doctor's TARDIS. (TV: The Doctor's Wife)

Behind the scenes
In the script for TV: The Doctor's Wife, writer Neil Gaiman described the junkyard as "the Totter's Lane at the end of the universe." (CON: Bigger on the Inside)