You could read about the underground submarine base - atomic shelter in Balaklava Bay in one of our previous articles, but this is a more detailed description supported by historical photos.
So, as you know, the construction was completed in 1963 and after the disintegration of the USSR the complex was passed on to the Ukraine where it had been plundered until they decided to turn it into a museum. In the picture you see its plan.
The complex contained from 7 to 9 submarines (depending on their size) and 300 members of the crew. It could also stand a 100-kiloton nuclear explosion.
The base consisted of a 600-meter long channel, a dry dock and working areas (storages, a metal workshop, etc.). The entrance to the channel and its exit were protected with special 120-ton and 150-ton gates.
Here they also assembled and stored ammunition (including nuclear). It had a soundproof system and climate and humidity control system.
Its fuel storage contained 9.5 thousand tons of fuel (mostly diesel). This part of the base is closed for visitors.
The walls are concrete and 1.5 meters thick. The maximum width of the rocky ground is 126 meters. The whole complex presents a system of independent underground constructions and passages connecting them, which are mostly bent to take up nuclear explosion shock waves.