The visitor discovering Saint-Romain-en-Gal must keep in mind the topography of Antiquity : between the 1st century BC and the 4th century AD, Vienna, one of the largest cities of Roman Gaul, covered the two banks of the Rhône.
The urban landscape was not the same on both sides of the river. The residential and commercial district developed on the right. Its vestiges can still be seen in Saint-Romain-en-Gal, which is classified as a historical site.
The political and religious center, as well as public entertainment sites, was situated on the left bank.