Belushya Guba

http://en.wikipedia.org/wiki/Novaya_Zemlya

"..in July 1954, Novaya Zemlya was designated the Novaya Zemlya Test Site, construction of which began in October[24] and existed during much of the Cold War. "Zone A", Chyornaya Guba (70.7°N 54.6°E), was used in 1955–1962 and 1972–1975.[24] "Zone B", Matochkin Shar (73.4°N 54.9°E), was used for underground tests in 1964–1990.[24] "Zone C", Sukhoy Nos (73.7°N 54.0°E), was used in 1958–1961 and was the 1961 explosion site of the 100 megaton (fired device was a downgraded design to 50) Tsar Bomba, the biggest nuclear bomb ever detonated.[24]"

There are 3 zones that were used by the Soviets to test their nukes but not a lot appears yet on satellites pictures.