In central Riga, the Soviet security services had their headquarters. First between, June 1940, and, July 2, 1941. Between July 1941, and September 1944, Riga was occupied by Germany and the headquarter was used by nazi collaborators. Second time lasted from September 1944 until the fall of the Soviet Union in 1991. The house was also called Corner house because it was located in the corner of the streets Stabu and Brivibas. Thousands of Soviet opponents were imprisoned and tortured in the basement of the headquarters. Even executions of latvians took place. For thousands latvians, headquarters became a staging point before being deported to labor camps in Siberia.

Current status: Preserved with monument (2010).

Address: Brivibas iela 61, Centra rajons, Riga, LV-1010.

Get there: Tram.

My comment:

When I was there in 2010, the former headquarters was not a museum but used by the local police, but is now a museum. In another place in Riga there is an interesting museum, the Museum of the Occupation of Latvia, which partly depicts the Nazi occupation of Latvia, partly the communist occupation. Its main focus is on the latter.

Follow up in books: Andrew, Christopher: The KGB (1990).