Bunker Alsou or object 221 (Protected Command Point of the Black Sea Fleet) is situated on the mountain Mishen in the Crimea, Ukraine. It is the biggest underground structure on the territory of the country except the subway.
The bunker had to become a reliable protection of the Black Sea command from a possible nuclear attack from the American side (Dropshot plan).
The bunker construction began in 1977. Mishen mountain represented a very solid monolith with no single fault. It was perfect for construction of a structure like this.
After the collapse of the USSR in 1992, the construction was almost stopped at the stage of 90% readiness. Then the object was started to be slowly plundered. They even exploded the object to get inside for gain.
The object has four levels: the main command level, residential level, hardware level and communication level, it also has two portals (eastern and western ones). The bunker goes deep into the mountain for 500 m (1640 ft) and lies at the depth of 180 m (590 ft) in the place of passage of a vertical shaft.