The Arch of Augustus stands on a rise in the western part of Susa, along what was the Via Cozia, today the via delle Gallie. King Cottius had it built between 9 and 8 BC to celebrate the foedus, the pact of alliance he had made with the emperor in 13 BC. Octavian Augustus himself came to inaugurate it, stopping at Segusium on his way back from Gaul.
What to see
It is a single-arch structure, 8.85 metres high and 5.85 wide, with a barrel vault and corner pilasters carrying Corinthianesque capitals; the whole construction reaches 13.07 metres in height. Four corner columns with fluted shafts, partly set into the structure, carry the entablature and produce a curious optical effect: from whichever side you look, you see two at each corner, and they seem to be more than four. Above the entablature runs the attic with the inscription. The material came from nearby: the limestone and marble blocks were quarried in the Foresto area, and Roman and central Italian artists worked on it alongside local craftsmen.
Visiting
The inscription is the thing to read. It runs to four lines, on the north and south faces, and was originally in gilded bronze letters: those vanished centuries ago, along with every other metal part, and today the text can be read only from the sockets that held them. It says that Cottius, holding the office of prefect, together with the fourteen peoples answerable to him, dedicates the arch to Augustus; and those peoples are listed one by one, from the Segusini to the Caturiges, from the Medulli to the Vesubiani. It is a written source that has come down complete after two thousand years.
Our editors' tip
Walk round the arch and look at the frieze, which runs the length of the entablature. On three sides it can still be read; on the eastern one time has corroded it past understanding, a good reminder of how lucky the rest is. The monument owes its condition partly to a careful restoration carried out for its bimillenary, between 1990 and 1992. One point of context: the Roman walls you see beside it were not there when the arch was built, being three centuries later.