Cumbria
Cumbria was an English county.
In 1207 Cumbria, the Eleventh Doctor stayed in a monastery to help in his search for "the woman twice dead", Clara Oswald. Clara rang the phone on the front of the TARDIS from 2013 to ask the Doctor about fixing her Wi-Fi. The Doctor left to find Clara. (TV: The Bells of Saint John)
The Tenth Doctor and Martha Jones went there in the 1950s. (COMIC: Agent Provocateur)
In 1994 the Second Doctor went to a haunted house in Cumbria with Ben Jackson and Polly Wright. (PROSE: Invasion of the Cat-People)
Behind the scenes
Several episodes aired in 2013 have featured references to Cumbria, constituting an apparent "Cumbrian agenda". It started with scenes actually set there in Bells, followed by The Rings of Akhaten having a reference to the Lake District. Hide later had two separate references: a rather negative one to Carlisle, and the Doctor's request to save Hila Tacorien with some sturdy rope and Kendal Mint Cakes.
Real World Locations
Though it's possible that the following locations don't exist in the same geographic space in the Doctor Who universe, such cases are few and far between. Therefore, the following towns and cities are probably located within the county of Cumbria.
Barrow-in-Furness | Carlisle | Cockermouth | Kendal | Penrith | Ulverston | Whitehaven | Windermere | Workington |