Built to honor the Roman Emperor Hadrian during his visit in Athens in 131 A.D. The arch is made of Pentelic marble and it is 18m high, 13.5m wide and 2.3m in depth. It is located 325m southeast of the Acropolis. It bears two inscriptions on each side. On the northwest side (facing the Acropolis) read: 'This is Athens the ancient city of Theseus' while on the other (facing the Olympieion): 'This is the city of Hadrian and not of Theseus'.