The defensibility offered by this unique geography made Caesar hasten to occupy Vesontio in 58 BCE. The town came to have all the usual Roman structures– forum, baths, aqueduct, and amphitheater (on the other side of the Doubs, to the northwest.) But the most visible remnant is the Porte Noire (Black Gate) [3], a triumphal arch built by Marcus Aurelius at the southeastern end of the cardo maximus, today Grande Rue and still the center of city life.
Archaeology in a downtown area is always a matter of seizing opportunities as they are presented by new construction, remembering and recording what was found, and coming back years later to complete the picture. A good example of this process is at our second site, [2] on the map. In 1973, the Neptune Mosaic was discovered in rue de Lorraine, one of the largest floor decorations in all Gaul. The extent of the mosaic under nearby buildings made full excavation impossible. More than thirty years later, in 2004, construction of a gymnasium for the Collège Lumière (a middle school) gave archaeologists access to much more of the site, about 3000 square meters, for a salvage excavation. As expected, the continuation of the Neptune mosaic was found; moreover, three other mosaics of high quality, along with columns, sculpted blocks, peristyles, and monumental pools came to light. The results of this excavation have not been published; we are grateful to the excavators for sharing their preliminary results.