The Arc de Triomphe d'Orange stands at the northern edge of town on the old Via Agrippa road from Arles to Lyon. Built around 27 BC under the Emperor Augustus, it is one of the oldest surviving Roman triumphal arches in the world and the model for many later examples. The triple arch — a tall central opening flanked by two smaller ones — became the standard form across the Empire.
The carved panels are unusually detailed: naval trophies, captive Gauls, weapons, and battle scenes celebrating Roman conquest of the region. It survived as a defensive tower in the Middle Ages, which is why much of the sculpture is so well preserved. Free to visit (it sits on a traffic roundabout but with a fenced pedestrian island), and a kilometre walk straight up Avenue de l'Arc de Triomphe from the centre. Together with the theatre, it forms the UNESCO World Heritage Site.