Porta all'Arco site features

The gate stands at the bottom of the lane that takes its name, on the south side of the town — and the first thing to register is that it is not a monument set aside. It is a working gate in a live street, with vehicles passing under it.

It is built of great blocks superimposed dry, without mortar, and what strikes you before any detail is the colour, because three different rocks are at work. The piers are a yellowish arenaceous limestone — the local pietra panchina; the arch is a grey reef limestone; and the three carved heads are reddish selagite. Yellow uprights, a grey arch, three red heads.

Those heads are the point. On the outer front they mark the three structural elements of the arch — the keystone and the two springing points — as protomes, worn almost featureless now. Their identification is open, and the competing readings are worth knowing because they change the mood of the gate completely: Jupiter with the city's two protectors, Castor and Pollux; or Jupiter with Uni and Minerva, protective deities; or a reference to the eastern custom of displaying the severed heads of enemy commanders on city walls, as a warning to any hostile presence. Gods welcoming you, or trophies threatening you.

Go through, and notice there are two openings, not one. The outer fornix — the one with the heads — was originally defended by a portcullis that allowed rapid closure; the inner one was barred by two leaves. Between them is a space, which is why the plan is described as a chamber: an attacker who got through the first opening was standing in a box.

Nearby, a bas-relief placed in 1984 records what happened here in 1944.

• The three carved heads (protomes) — in reddish selagite, marking the keystone and the two springing points of the arch on its outer front, and open to three competing identifications.
• The three rock types — yellowish pietra panchina in the piers, grey reef limestone in the arch, reddish selagite in the heads: the gate's lively colouring is structural, not applied.
• The dry-laid great blocks — set one on another without mortar, part of the city's pietra panchina Etruscan circuit.
• The chamber plan — two fornices: an outer one originally closed by a portcullis for rapid defence, an inner one barred by two leaves, with a space between them.
• Its survival from Roman reworking — it suffered less than comparable gates in other cities, and so still has the grandiose imposingness typical of Etruscan city gates.
• The 1984 bas-relief — placed near the gate to commemorate the rescue of 30 June 1944.
• Its position in the road network — the principal southern access, opposite the Porta Diana to the north, and the gate from which roads ran to the Val di Cecina, the salt-pans and the Colline Metallifere.
• The 19th-century copy elsewhere — a reproduction of this gate was built as the entrance to the castle of Rosazza by Giuseppe Maffei, architect and painter of Graglia.