During the First World War the front line ran through Mount Lagazuoi, and the Italians and Austrians dug tunnels through the mountain to try and plant mines underneath their enemy. Those tunnels have been restored and the walk down them has been designated Via Ferrata Lagazuoi Tunnels.
Begin by taking the cable car from the pass to the top of the mountain. Then follow the marked path along a ridge to the mouth of the tunnel. Torches and a helmet are essential.
There are several side galleries that you can explore and reconstructed living quarters for the soldiers. There are several places where the tunnels open on to the side of the mountain. The tunnels finish part way down the mountain and it is then a matter of following a clearly marked path back to the pass.
Some people insist on walking up rather than down, though none of them seem very happy about their choice as you pass them on your way down.
A better choice is to spend the night at Refuge Lagazuoi, and then start the day by the walk down the tunnels.