The Library

The Library was a planet-sized library that was built during the 50th century. It contained every book ever written. Within its core was the largest hard drive ever, which served as an index computer, as well as containing backup copies of every book ever written. The planet had one moon, which was actually an antiviral subroutine having the physical appearance of a moon. Due to its caretaking role, it was known as a Doctor Moon.

Creation
The Library was commissioned by Felman Lux and was managed by a head Librarian. Visitors to the Library used courtesy nodes, sculpted computer terminals containing real faces made from donated flesh. The security were levitating wooden spheres. Visitors were advised to switch off their mobile comm units.

Paper editions of every book ever written were made specially for the Library. Unfortunately, the forests cut down to make the books were home to Vashta Nerada, which then hatched from the books and infested the Library. The computer managed to "save" all 4022 visitors to its hard drive, where they could dream an imperfect virtual existence.

Arrival of the Doctor and River Song
The computer sealed off the planet, and it would be 100 years before the Lux family could arrange an archaeological expedition led by Professor River Song.

The Doctor and Donna Noble arrived after being asked to come by River Song, via his psychic paper. (DW: Silence in the Library) The Doctor helped to return the visitors and agreed with the Vashta Nerada to make sure no one arrived in the Library again. (DW: Forest of the Dead)

Later visit by the Doctor
The Doctor and Amy Pond later visited the Library, where they encountered the Book Monsters. (DWA: Booked Up)