SEGUSIO (mod. Susa, q.v.), an ancient town in north Liguria, the capital of the Cottii (see Cottii Regnum). Here the son of King Donnus, Cottius—who held the rank of imperial praefect over the fourteen tribes over which his father had ruled as king, so that in the inscription he calls himself “M. Iulius regis Donni f(ilius) Cottius praefectus civitatium quae subscriptae sunt”—erected a triumphal arch in honour of Augustus in 9–8 B.C., which is still standing. The style of the sculptures on the frieze is quite barbaric, with archaic elements, and is probably derived from Gaul. His tomb, situated near the city walls, mentioned by Ammianus Marcellinus, has long since disappeared. Claudius restored the royal titles to the family; but, after the death of its last member, Nero made the district into a province, and the town into a municipium. It was strongly fortified and garrisoned, and remains of its walls, including those of a double-arched gate, exist, while inscriptions testify to its importance, one of them mentioning baths erected by Gratian. Constantine captured the town, which offered some resistance to him, on his march against Maxentius.
See F. Genin, Susa Antica (Saluzzo, 1886); E. Ferrero, L’Arc d’Auguste à Suse (Turin, 1901); F. Studniczka, Jahrbuch des K. D. archäologischen Instituts, xviii. (1903), 1 sqq. (T. As.)