Cardiff Space-Time Rift

The Cardiff rift was a time rift in the city of Cardiff, in Wales.

History
The rift was created at the dawn of time where the Earth would later form, using it to imprison Abaddon, The Beast's son for all eternity. However, unlike The Beast's trap, Abaddon could easily be freed if the rift was opened. (TW: End of Days)

The rift was known about by other races before 1869 and had caused psychic powers in people in the area (such as Gywneth's clairvoyance). It was also known by the Gelth, a gaseous race which had their physical bodies destroyed during the Time War. They went through it to try and take over the bodies of dead Humans, and then eventually attempt to invade the planet and kill all Humans for their entire species. During this attempt, the time rift was partially sealed by an explosion over it. (DW: The Unquiet Dead)

The rift was later used in September 2006 by both the Ninth Doctor and Blon Fel-Fotch. Though the Doctor used it to refuel the TARDIS, Blon Fel-Fotch, now mayor of Cardiff, built a nuclear power station on it and attempted to cause a meltdown, which would destroy the Earth and give her a chance to escape. (DW: Boom Town)

The Torchwood Institute also set up a Wales branch, Torchwood 3, led by Captain Jack Harkness after they became aware of the Rift. Subsequently the rift has created a perception filter where the TARDIS landed and has been a hotspot for alien activity, but became more active after the opening of the rift and the death of Abaddon. (TW: Everything Changes, Captain Jack Harkness, End of Days)