The Gallo-Roman sanctuary of Champlieu is located about 15 km south of Compiegne. Classified as a historical monument since 1846, the site was discovered in the sixteenth century. Excavations were undertaken under the Second Empire by Viollet-le-Duc. There was a Gallic sanctuary and perhaps a military establishment during the Roman conquest. The ancient name of the city is unknown, but it would have been a conciliabulum, a forum. The latest Roman currency on site dates from Emperor Zeno (reigned 474 to 491). There were baths, two temples and a theater. In the mid-second century, the horseshoe-shaped theater was built, 70 m in diameter with seating for up to 3,000 people.