Communication Y, Military monument in Briançon, France.
Communication Y is an underground vaulted passage that connects two mountain fortresses and stretches about 200 meters long. The corridor is about 4.5 meters wide and was built with a barrel vault roof to provide shelter and structural stability.
The first design for this passage came in 1711, but was later reworked before construction began in 1724. The work took about ten years to complete and was part of the wider fortification system protecting Briançon.
This underground passage was part of a carefully planned defensive system that engineers designed to protect the city of Briançon. It shows how military planners thought through every detail of protection.
Access is typically through organized tours that lead through the underground passages and explain how they function. It is helpful to wear flat shoes since the ground can be uneven and the passages are narrow.
The passage contains a clever water system with a collection basin that stored spring water for the entire fortress complex. This feature shows that engineers thought about daily needs for the garrison, not just defense.
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