Pandorica

The Pandorica was a prison box, hid under Stonehenge, constructed to hold the most feared organism in the history of the Universe. It was mentioned by Prisoner Zero to the Doctor and told him that it would open and that silence would fall. (DW: The Eleventh Hour) River Song also mentioned the Pandorica to the Doctor, telling him she would next see him there and that she remembered it well. The Doctor believed at that time that the Pandorica was a fairytale. (DW: Flesh and Stone) The Pandorica turned out to be a prison, built possibly by The Alliance for the Doctor to stop him from destroying all universes. Their conclusions held that the Doctor would be responsible for the destruction of existence itself and thus used the lure of the Pandorica in order to entrap him. (DW: The Pandorica Opens)