Panorama Photo

I would be very surprised if someone guessed it. There is no indication for this construction, it is dangerous to enter it and it is almost unknown even to those who live nearby. But once ...
This was the entrance. The construction was very much larger.

SOLVED RIDDLE.

The construction of Forte Bastione dates back to the second half of the 1800s with the aim of protecting the naval base of La Spezia (which was the main Italian naval base). In its first decades of life not a single shot was fired and during the First World War it was used as a prison camp for Austrian prisoners.
During the last years of the Second World War it was a cornerstone of the Gothic Line and used by the German army as an artillery observatory to cannon the Allied armies attempting to climb the Peninsula. During this period it was the scene of fighting and suffered severe bombing which destroyed various parts of the fortress. Conquered and occupied by the Allies, it quickly lost all military utility and was abandoned: since then it has been in ruins.