Cardiff City Hall

Jack Harkness stood atop the Cardiff City Hall when he received a phone call from Owen Harper, telling him there was something he needed to see at the Torchwood Hub. (TV: Greeks Bearing Gifts)

Behind the scenes
Though the building is not named in Greeks Bearing Gifts, it is irrefutably recognisable from the many angles given.

In Boom Town, Cardiff has a Town Hall, which looks totally different.

The real Cardiff City Hall has been used for location filming in many episodes of BBC Wales Doctor Who, including Blink and The Doctor's Daughter. It filled in for the White House in The End of Time, and for interior Buckingham Palace in Voyage of the Damned.