The Tour du Lépreux stands at the northwest corner of the original Roman perimeter wall, where it has stood since the city was founded in 25 BC. The lower courses are Roman concrete and granite, while later medieval additions rise above them — the tower was never entirely abandoned, which is the main reason it survived. It stands to a height of around 20 metres and is one of the most complete of Aosta's surviving Roman towers.
The macabre detail of its name comes from the medieval period when the tower's upper room was used to confine a sick man named Georges Groulart, who according to local records spent years in isolation there, supplied through a small opening in the wall. The tower sits on the rue Jean-Boniface Festaz, on the western edge of the old city, slightly removed from the main tourist circuit. It is worth a short detour to see the Roman masonry at close quarters and to understand the full extent of the original fortifications.