Todi has a triple ring of defensive Walls. The first circle is dating Umbrian-Roman, remains are left mainly near the Marzia Gate. It underwent modifications in the XVII century. Another set of Wwalls can be seen near the Lower Valley (also called the Lucretia), locally called "Etruscan Wall" (improperly, since Roman times) is one of the most impressive works of ancient Todi: has two tunnels (less and higher), built for hydraulic purposes and still functioning. The third circle was completed in 1244, and reached the present day intact through several restorations. About 4 km long, is equipped with doors fitted with battlements and buttresses. The Gates are named after the city of destination.