This central city gate was built in the 3rd century A.D. by the Roman Emperor Vespasian.
More than anything this was a monument. There were a number of statues decorating the gate. Most of these statues were dedicated to the emperor.
It is a 9 m. wide and 12 m. high, arched gate next to the Theater, the Agora and the Vespasian Monument. The main road to the harbor was going through this monumental gate.