The Valdarno area contains these landscapes with pinnacles and spires, which, as in Bryce Canyon in Utah, were formed from sediments deposited by a lake in the Pliocene and Pleistocene, about 20 km long, that occupied the entire area.
The rocky pinnacles and spires, which give the Valdarno crags their name, are up to a hundred meters high and consist of layered sands, clays and gravels of diverse shapes, intertwining in deep gorges.
In Castelfranco di Sopra (Ar) there is a loop trail, already marked by CAI and called "dell’acqua zolfina," where it is possible to admire up close one of the most beautiful views of the Balze del Valdarno.
The trail is about 6 km long in an alternation of unique scenery. The starting point is just outside the village walls, near the post office where in a small wooden tabernacle the entire itinerary is minutely described.
