LONDON — Archaeologists have discovered the well-preserved remains of a Roman neighborhood that was destroyed early in the first millennium after Christ, in what the French Culture Ministry called an “exceptional discovery.”

The neighborhood was found near Ste.-Colombe, a suburb across the Rhône River from the city of Vienne, about 20 miles south of Lyon. Vienne is well known for its traces of Roman civilization; several old city ramparts survive, as do the remains of a theater and several roads.

Benjamin Clément, an archaeologist with Archeodunum, a company with offices in Switzerland and France that evaluates historic sites that could be threatened by construction, called the discovery “probably the most exceptional find from the Roman era in years.” Work on the site began in early April, and reporters were permitted to visit the excavation for the first time this week.