Entremont, the political capital of the Celto-Ligurian Confederation, was a city open to trade.

Archaeological excavations and the statuary exhibited at the Granet Museum bear witness to its advanced civilisation. In 122 BC the Romans abandoned the plateau of Entremont to settle on a site rich in resources: Aquae Sextiae (the waters of Sextius) was born. Having become a Roman colony, the town was a stepping stone between Italy and Spain, and developed as an urban centre and spa. With the spread of Christianity, a new leaf was turned.

A diocese from the start of the 5th century, and with the palace of the Archbishop of the ecclesiastical surrounding area, Aix also claimed its Capital rights.