The wall built over thirty years was probably completed in the middle of the 4th century. The perimeter wall was 1245 m long, encircling an area of 9 hectares. A series of towers, of which the museum retains a corner tower (originally it could reach the 30 m. with its covering) regularly reinforced the rampart partly built with salvage materials, from public buildings and temples of the second century (columns, entablatures, carved fragments...). The eastern part of the enclosure, formed by the former amphitheatre (1st century), is visible on the terraces of the museum garden. Transformed into a fortress in the 3rd century, the amphitheatre is integrated into the defensive rampart of the Lower Empire, rampart, of which it constitutes the structuring element, in the first half of the 4th century. Its location on top of a small “hill” on the edge of the ancient urbanized area, protects it from flooding, facilitates traffic around it and signals it from afar as an ostentatious symbol of the city’s power. Building of massive structure and substantially elliptical shape, its estimated dimensions are then 122 m by 94 m. Enlarged in the 2nd century (156 134 m), it becomes one of the largest of all the Roman Empire to the point of being sometimes called «architectural monster», and in the twenty-first century its colossal dimensions cannot be explained in terms of the size of Caesarodunum and the city of Turons. This wall will be reused, except for its western flank, in several successive enclosures of Tours, the extension of the enclosure to the 12th century and the 14th century. The Gallo-Roman rampart has been partially inscribed as a Historic Monument since 1927. Below the western part of the rampart is the museum’s underground. It was certainly started by the canons of the cathedral to recover materials, but especially to store food. Cellar, reserve, the underground was also dungeon, in order to put some indelicate characters on ice. Many graffiti and carved pieces (bird, crests, coat of arms of Tours, devil’s head...) testify to this. Finally, here is still visible the only Latin inscription of the independence of the city of Tours: "CIVITAS TURONORUM LIBERA", the free city of Turons. All the fragments of these inscriptions would be a dedication of the city to the Roman emperor Claudius and his sons, Tiberius Claudius Drusus and Britanicus, inscribed on the walls of a temple erected in honour of the emperor following the conquest of Brittany around the year 50.