Back in USSR...

The bunker was erected in 1928, it has two floors: the upper floor with three MG casemates for 7.62 "Maxim" machine gun and the bottom floor with a crew's shelter, warehouse, airing system and electric generator. Garrison of the bunker consisted of 11 people (commander, mechanic, and three machine-gun crew of three soldiers in each). The thickness of the walls and ceilings - up to 1.5 meters.