Built by Soviet Union in 1962, Plokstine nuclear underground missile base was one of the first of it’s kind. Discovered by US only in 1978 it covered whole Europe including Turkey. Today the base is used as a cold war museum.
It’s missile silo was composed of an outer concrete cylinder of 30m in depth and 7m width, and an inside steel cylinder of 5m diameter. The silo had a protective hood to be closed if required and 6 technological floors with different tasks.