The Czech Republic was a country in Europe. It broke away from Czechoslovakia at some point in the late 20th century, as did Slovakia. Its capital city, Prague, was visited by the Doctor in most of their known incarnations, at various points in its history. (PROSE: Life from Lifelessness, Spoilsport, The Dragons of Prague, Suspension and Disbelief, Leap Second, Sunday Afternoon, AD 848,988, Fable Fusion, War in a Time of Peace; COMIC: The Broken Man)
History
InterCom had research facilities in the Czech Republic. There, they had been looking, unsuccessfully, for human candidates that possessed DNA appropriately resistant to their late-1990s DNA-extraction project headed by Chung Sen. (PROSE: The King of Terror)
In August 2016, Mickey Smith was busy doing something in the Czech Republic while his wife Martha Jones investigated the Gargoyles in San Francisco. (COMIC: The Transformed)
The Czech Republic and Slovakia were still separate countries as late as the 22nd century. (PROSE: Life from Lifelessness)
In the 22nd century, the Wronsdehj conquered the Czech Republix, along with Poland, Austria, Germany, Italy and France. They were eventually defeated by the Fourth Doctor and Romana I. (PROSE: Life from Lifelessness)
In the 23rd century, Slovakia and Czechia were again united as the Third Czech and Slovak Republic. (PROSE: Spoilsport)