The board informing you about Buco di Viso, which was the first ever man-made tunnel in Europe, built in 1479. The lowest bit is one metre fourty high, but the entrance is a lot smaller. You have to take of the backpack to get in and you don't see anything for a while. There is also snow inside. And it is a major tourist attraction. There were loads of Sunday walkers that came up from Pian del Re just to tackle THE HOLE.