No visit to Moscow would be complete without a quick visit to what was, for much of the 20th century, the most notorious building in the world. The bland, bulky sandstone building was originally built as the headquarters of an insurance company in 1897. However, after the revolution it became the headquarters of the KGB, and the epicentre of that nefarious organisation's reign of terror over the city during Stalin's time. There are headquarters of FSB (Federal Secure Service) inside this building nowadays.