Sestri Levante has its origins as an ancient maritime and merchant center. Originally a small island with a promontory, it was later connected to the mainland. In Roman times, it was known as Segesta Tigullorum (or Tigulliorum) or simply Segesta, but the place was nearly abandoned when the Roman empire collapsed. It seems to have belonged to the Ligurian tribe of the Tigullii. It was mentioned again in the year 909 in a certificate of Berengar I of Italy, in which part of its territory was ceded to the basilica di San Giovanni di Pavia. During the Middle Ages, Sestri Levante began to expand, probably giving the fortress appearance that is due to the terrain.