Carlisle

Carlisle was an English city that Clara Oswald once called, and the Eleventh Doctor agreed was, the "opposite of bliss". (TV: Hide) It was famous for its Roman wall, for which Ian Chesterton may have been partially responsible. While a slave in 64, he tried to ingratiate himself to General Gaius Augustus Calaphilus by suggesting that the Roman "try building a great big wall from Carlisle to Newcastle" to keep the Scots out. (PROSE: Byzantium!)

The town also had a bit of significance to Jamie McCrimmon. Not counting McCrimmon himself, the second-most-travelled person in his home village in the Scottish Highlands could only boast as having gone as far as Carlisle. Prior to Jamie's life in the TARDIS, Carlisle evoked a sense of being "far away". (PROSE: Twilight of the Gods)

Emergency services
George Smithers knew that, at one point, there were two concrete police boxes in Carlisle. Also, the city was close enough to the seaside village of Whitley Bay that policeman Gordon M. McGarry identified Carlisle as the provider of ambulance service to the village in the mid-20th century. (PROSE: Invasion of the Cat-People)

Commerce
In the 20th century, trains from Euston station to Carlisle and Sellafield changed at Preston. (PROSE: Invasion of the Cat-People)

Harwood's Haulage, Rhys Jones' employer, operated out of Carlisle, Ipswich, Sheffield and Cardiff. (TV: Kiss Kiss, Bang Bang)