Dominating the left bank of the Gapeau at an altitude of 349 metres, the site was excavated between 1972 and 1974. The Castellas is a fortified perched Iron Age settlement composed of huts and small workshops or sheds. It covers more than 5 hectares and is one of the largest oppida in Provence. The surrounding wall must have had about fifteen towers and two monumental entrances. A few dwellings have been excavated inside the first enclosure. The presence of archaic grey ceramics and Etruscan amphorae attests to an occupation of the site from the 5th century BC or even the end of the 6th century. The dwellings partly excavated in the second enclosure can be dated to the 2nd and 1st centuries B.C.
History of the oppidum: from the 3rd century onwards, the Romans, victors over Carthage, extended their hegemony over the western Mediterranean basin. Between 197 and 189 BC, they received the submission of the various Gallic Cisalpine tribes. In 57 BC, Julius Caesar pacified almost all of Gaul. Two centuries later, the Castellas oppidum surrendered. As far as the Gapeau valley is concerned, and more specifically Solliès-Toucas, the first human settlement was located on the heights of Castellas to the north of the village. It dates back to the second century BC. Historians tell us that the Gallic religion practised there was the worship of two deities: Teranis, the god of lightning, and Teutates (Toutatis), hero of the warriors. The chief Druid (Prinium) maintained a climate of fear for any breach of these doctrines; there were many rituals to obtain the sun, rain or valour. Once a year, in spring, the priests made a sacrifice in honour of Teutates: they offered him a human victim. Another less cruel ceremony was the gathering of mistletoe. Practised at the beginning of winter, the officiants, all dressed in white, went in procession to cut the "magic" berries on the northern slope of the Castellas.