- Total distance: 4 km- Vertical descent: absentAmong the tunnels dug into the rock, in absolute darkness, we will talk about a technological jewel of the ‘900, a flagship of central Italy that in the ’70s was dismantled. Between friends and chit chats, we will analyze the rocks surrounding us and finally we will go up in altitude to see the Valnerina from above and, if we are lucky, we will also witness an excellent sunset.Join this walk with your family and friends to live a day full of discoveries on the tracks of history, nature and geology in an anjoyable and compelling experience.