Wales

Wales is a small principality west of England, part of the UK. The capital and largest city in Wales was Cardiff.

Historical events

The Doctor and Jo Grant visited a mining area in Wales in the 1970s. (DW: The Green Death)
In the 1950s a Navarino group together with The Doctor and Melanie Bush crash at a holiday camp in Wales. (DW: Delta and the Bannermen)
A time rift is located in Cardiff, which The Doctor has used to refuel his TARDIS a number of times. (DW: Boom Town, Utopia)
Torchwood 3 was located in Cardiff, primarilly to monitor the aforementioned rift (TW: Everything Changes et al. )
Gwen Williams' family were from Swansea
The members of Torchwood 3 investigate a series of murders in the Brecon Beacons. (TW: Countrycide)
Gwen Cooper visited Aberystwyth University when investigating the death of Eugene Jones. (TW: Random Shoes)

The revived series of Doctor Who, as well as all seasons of Torchwood and The Sarah Jane Adventures were produced and filmed in Wales, with most of the latter taking place in and around Cardiff.
Location filming for The Abominable Snowmen and The Five Doctors were filmed in desolate-looking areas of North Wales while outside shooting filming The Masque of Mandragora was done in Portmeirion, also in North Wales.