Cheka, GPU, NKVD and KGB are all names designating the same Soviet secret police that terrorised, tortured and executed all opponents of the regime considered - rather hastily - to be "counter-revolutionaries" or spies. It was located in a building overlooking Lubyanka Square! Needless to say, the area is not exactly packed with tourists. But its lively little streets, on a very human scale, contain treasures such as the Mayakovsky Museum and some fine palaces (Apraksin House).