The earliest surviving architecture in France dates to the Stone Age, as a number of prehistoric sites in Brittany attest. Classical architecture was introduced into the south of France during the Roman conquest in the 1st cent. A.D. Well-preserved examples of Roman architecture include the Maison Carrée and the Pont du Gard near Nîmes. Scant traces remain of the early development of Gallic architecture, including Early Christian, Merovingian, and Carolingian buildings. The Roman basilica form predominated and, during the Carolingian period, was greatly enriched by design innovations.