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 Doctor was drawn to the bubble universe by a distress hypercube from the Corsair. (DW: The Doctor's Wife) Though in reality it is nothing like a bubble universe, in an effort to explain to Rory why they could leave the universe when the universe is everything that exists the Eleventh Doctor replies "imagine a great big soap bubble with one of those tiny little bubbles attatched to the side", "okay", "but its nothing like that".