The Ligurians were in this area from about 800 BC. Later Celtic influences have been discovered. The city became an important Phoenician trading port, before being taken by the Romans.
The Romans took the town in 123 BC and expanded it into an important city, with a canal link to the Mediterranean Sea being constructed in 104 BC. However, it struggled to escape the shadow of Massalia (Marseilles) further along the coast.
Its chance came when it sided with Julius Caesar against Pompey, providing military support. Massalia backed Pompey; when Caesar emerged victorious, Massalia was stripped of its possessions, which were transferred to Arelate as a reward. The town was formally established as a colony for veterans of the Roman legion Legio VI Ferrata, which had its base there. Its full title as a colony was Colonia Iulia Paterna Arelatensium Sextanorum, "the ancestral Julian colony of Arles of the soldiers of the Sixth."
Arelate was a city of considerable importance in the province of Gallia Narbonensis. It covered an area of some 99 acres (400,000 m²) and possessed a number of monuments, including an amphitheatre, triumphal arch, Roman circus, theatre, and a full circuit of walls. Ancient Arles was closer to the sea than it is now and served as a major port. It also had (and still has) the southernmost bridge on the Rhone. Very unusually, the Roman bridge was not fixed but consisted of a pontoon-style bridge of boats, with towers and drawbridges at each end. The boats were secured in place by anchors and were tethered to twin towers built just upstream of the bridge. This unusual design was a way of coping with the river's frequent violent floods, which would have made short work of a conventional bridge. Nothing now remains of the Roman bridge, which has been replaced by a more modern bridge near the same spot.
The city reached a peak of influence during the 4th and 5th centuries, when Roman Emperors frequently