After its occupation during the alps campaign of 16/15 BC the Wallis was reorganized. The four tribes (Nantuater, Veragri, Seduner and Uberer) were left in their unity. Each of it was divided into a civitas (municipality). The alpine region formed an administration unit with a military commander.

In the year AD 47 the four civitas were combined in a single one, the Civitas Vallensium. Capital became now the new set up Forum Claudii Vallensium. The former capital was Tarnaiae (Massongex) with its federal sanctuary of the four tribes.

Following was the civitas split off the formerly set up province Raetia and combined with the regions around the Big (Alpis Poenina) and Small St. Bernhard (Alpis Graia) the province Alpes Graiae et Poeninae. Capital of the province became Axima (Aime-en-Tarantaise).

Forum Claudii Vallensium was set up near to the Celtic settlement Octodurus, today not localized still. The new town area was still before unsettled. The name of the city was, according the founder Tiberius Claudius Nero Germanicus, Forum Claudii Augusti. Later followed the renaming in Forum Claudii Vallensium.

The city was put on chessboard-like. Several insulae existed. Some buildings (for example a temple), in particular in the northwest, were not aligned to this structure.

According to the importance of the place relatively many public buildings existed: 2 Gallo-roman temples, 1 nimphaeum, 3 thermal springs, 1 forum, 1 podium temple and 1 amphitheater. Later was built a Mithraism too.

The vicus was obvious spared of the Germanic raids of AD 259/260. At the middle of the 4th century the place was left more and more. The settlement concentrated itself then on the site of the old Octodurus which was possibly named now Octodurum.

Today still some remains are to be seen: Archaeological park (thermal springs, houses), two domus, temples and thermal springs in the Fondation Gianadda, a Mithraism sanctuary, an amphitheater and 1 milestone.