Was opened in the 13th century (although originally there was another door known as Porta Interocrina, from the ancient name of the current Antrodoco village) and takes its name from the Roman fortifications (called “arci”) that once defended the Via Salaria (Salt Road). The door had a considerable strategic value so that, in 1372, by order of the bishop of Lucca, a fortress was built here with the aim of improving the checking of people when entering and exiting the city.
For traffic needs, vehicles pass daily under it. Looking at the door from the inside, on the left it is possible to see a fountain.
Porta D’Arci has a very regular shape, a massive tower in the shape of a crenellated parallelepiped with a round arch that constitutes the upper part of the door, and other two round arches in the back, one above the other. In the front it is also visible a small opening at about two thirds from the top.