After the fact that a female Russian blogger had visited the "no trespassing" territory of Rocket Engine plant Energomash in Khimki for five nights in a row taking pictures of everything she saw (the plant's fence and guarded perimeter was torn down and there were absolutely no guards inside the territory) surfaced, it was expected that it would become impossible to visit the plant anymore and visits would be stopped. Yet a year after the incident nothing's changed. Welcome to another bomb shelter of Energomash!
Its emergency exit.
As a rule, the length of such tunnels depends on the height of the building above. It is made to provide that the exit won't be buried by the debris of the destroyed building.
The tunnel ends with this hermetic door.