The city of Autun, founded at the end of the 1st century BC under the reign of Augustus, although in the midst of a period of Roman peace, was equipped with a rampart from the outset. The construction of this fortification was primarily honorary. It is a rare privilege granted by the emperor himself to the capital of the Aedui. With a length of 6 kilometres, it encloses the urban space which is established on a strongly inclined ground of a surface of 200 hectares, which is delimited on all sides by a whole of water courses. In this context, the curtain wall, with an average width of 2.50 m, also plays a technical role as a retaining wall, holding back the earthworks of the terraces on which the buildings are located.
More than two thirds of the fortification has been preserved, an exceptional state of conservation for a structure of this period. It is composed of alternating curtain walls and 57 circular towers of about ten metres in diameter (30 towers are still visible). It is pierced by four monumental gates with four bays at the mouth of the main streets (3 of them are partially preserved: the Arroux gate, the Saint-André gate and the Saint-Andoche gate) and probably by several posterns, some of which were recently located thanks to the interventions of the Archaeological Service of the City of Autun, in particular in the vicinity of the theatre and the amphitheatre. Each of the streets of Autun, which intersect at right angles in a regular grid, leads to a tower of the rampart.
At the end of the 3rd century, the southern tip of the ancient city was enclosed over an area of about ten hectares by a small enclosure, which was gradually extended during the Middle Ages. The fortified "upper town" was home to the episcopal group. It is entered through a monumental gate, the remains of which dating from the 12th century are preserved on rue des Bancs below the Rolin Museum.