Part of the ancient ramparts and at the same time a watchtower over the Via Domitia linking Italy to Spain, the Tour Magne was a major part of life in the Roman City. The tour is illustrated with banners and cultural information boards explaining the history of the monument and the importance of the Via Domitia. From the top of this tower, where there is a striking panoramic view over Nîmes, the visitor can discover the city as it was in Roman times thanks to a big display board.

The Great Tower, is the only one left standing from the ancient city walls built by Augustus. It was
constructed at the highest point of the city, Mont Cavalier. It dominates the whole plain and is a focal point for lines of communication.
Originally, it was an oval dry stone tower similar to the one in the neighbouring oppidum of Nages at a maximum height of 18m and already part of a rampart.
Both a prestigious and strategic building at the same time, it marked the location of a sanctuary and protected the oppidum.
By doubling its height and incorporating it into the city walls, Augustus highlighted the new power of the colony of Nîmes over the "City" (in the territorial sense) of the Volques.
When the city abandoned the high ground, Tour Magne still continued to play a military role. It was used as a defence against the English during the Hundred Years War.