Syldavia

To get into the Soviet embassy in Prague, the Eleventh Doctor used his psychic paper to claim that he was the ambassador of Syldavia. (COMIC: The Broken Man)

Behind the scenes
Syldavia is a kingdom within mythos that sits roughly in the area of Transylvania and Moldavia. The use in the Eleventh Doctor comic, The Broken Man, is an obvious tip of the hat to the fact that then-show runner Steven Moffat wrote the 2011 film,.