The Brégançon site is listed as an archaeological site. However, unlike the other ancient cities of the Mediterranean coast, Brégançon was not mentioned during Antiquity, except in the form of Pergantium by the Greek geographer Stephanus of Byzantium in his dictionary of the 6th century AD. The remains found by archaeologists both on the islet of Brégançon and on the neighboring coast do not allow researchers to confirm the past existence of a town. They mostly tend towards the presence of a prehistoric enclosure, a Ligurian oppidum first transformed into a fortified castle in the Merovingian period then into a medieval fortress.