The Architectural Reconfiguration System is the fourth level of Bigger on the Inside prologue.
Fifth Doctor: We have to move fast. All it would take is the virus deciding to open the exterior door, flushing us out into the time vortex. And it would be game over for not just us, but for all of reality!
The TARDIS control room lights start to flicker.
Ninth Doctor: What the...
Suddenly the molecules of the TARDIS interior warp around the Doctors and their allies, the 12th Doctor's control room is replaced by...
(Scene shifts to the First Doctor's control room)
First Doctor: Much better, I could never think properly in the other one. Too busy. *chuckles to himself*
Rory Williams: I don't understand.
The control room shifts once more, back into the 12th Doctor's version.
Amy Pond: This is not good, not good at all. Doctor?
First Doctor: No need for alarm. The infinite space inside the TARDIS, every inch, every atom, is controlled by the ship. The TARDIS's architectural reconfiguration system can make anything reality -- anything it commands this space to be, will be.
(Scene shifts to the Library)
Tenth Doctor: It's ok, don't panic. We're not really in The Library, we're still in the TARDIS. She's just pulled this location from her memory banks, the virus is making her do some very strange...
(Scene shifts to Trenzalore)
Tenth Doctor: ...things. Let's hope at some point we get back to the TARDIS control room.