Pandorica

The Pandorica was a prison hidden under Stonehenge. It was built to hold the Doctor and ensure the safety of The Alliance.

History
According to legend, the Pandorica was the prison of a warrior or goblin who dropped out of the sky and tore the world apart until a good wizard tricked it and locked it up. (The Pandorica Opens)

The Pandorica was actually a prison built by the Alliance for the Doctor to stop him from destroying every universe. They believed the Doctor would be responsible for the destruction of existence itself. They used the lure of the Pandorica to trap him. There were many layers of security in the Pandorica including deadlocks, time stops and matter lines. It even had a restoration field to stop the Doctor from dying, which the Alliance believed a form of escape. (DW: The Pandorica Opens)

It was used to save Amy Pond. She was locked inside it for eighteen hundred ninety-four years until revived by her younger self. Her DNA provided the Pandorica the material it needed to fully revive the nearly dead adult Amy. During this time, it was moved several times. It was once put into storage in a London warehouse which was destroyed by the Blitz in 1941. It was dragged to safety from the burning warehouse by Rory Williams, and found a short distance away, unscathed.
 * 118 - Taken back to Rome under armed guard.
 * 420 - Plundered by the Franks.
 * 1120 - Prized possession of the Knights Templar.
 * 1231 - Donated to the Vatican.
 * Post 1231 - Sold by Marco Polo.

The Pandorica was also used by the Doctor to restore the universe. Since all of the traps inside it provided the perfect barrier against the destruction of the universe, it retained several billion atoms of the original universe within, even after the destruction of the rest of creation. Operating on the same principle as cloning a body from a single cell, these atoms provided a "blueprint" for the universe when the Doctor piloted it into the exploding TARDIS which had cracked all of time and space. The atoms from the Pandorica combined with the energy of the TARDIS's explosion to restore every point in time and the universe. Doing so caused the cracks in time to close and allowed Amy to remember her family and the Doctor - all erased by the cracks - back into existence. (DW: The Big Bang)

Exterior
The Pandorica looked like an image of Pandora's Box found in Amy Pond's bedroom. Since The Alliance used her memories to lure the Doctor there, they probably designed it to look like this. (DW: The Pandorica Opens)

Interior
The interior was a small room with a chair in it. When someone was placed on the chair, the exterior would close, sealing them in. Many forms of security would stop the prisoner escaping, presumably because the Alliance considered it too risky to allow the Doctor to remain conscious during his imprisonment. (DW: The Pandorica Opens)

Known inhabitants
The Eleventh Doctor was put in the chair by the Alliance to stop him from destroying the universe. Using the sonic screwdriver given to him by a future version of the Doctor, the Auton copy of Rory Williams opened the Pandorica and released him. (DW: The Pandorica Opens)

The Doctor and the Auton duplicate of Rory put Amy in the Pandorica while she was dying. She was restored when her seven-year-old self touched the box, causing it to open. Using its restoration field, the Pandorica resurrected the older Amy after it got a DNA sample from the young Amelia. (DW: The Big Bang)

Behind the scenes

 * For the Doctor Who Experience (London/Cardiff) part of the interactive story featured a device called the "Pandorica II". The Alliance trapped the Doctor in it again and it was up to the guests to bring the Tardis to him, so he could escape. The Doctor considered the Back Up Pandorica as cheating and complained on the fact that it wasn't even a different colour.