Abandoned two-level Czechoslovak infantry bunker for 17 soldiers from 1936, today in deep forest

At the time of construction (1936), there wasn't a single tree in the area. Today, a series of bunkers is surrounded by a deep forest and nearly century-old giants. Two are accessible like this one, two are locked with massive steel bars, one is maintained by a group of enthusiasts and filled with period equipment and decorations, two are concreted and probably ruined inside.