The commercial Agora was first built during Lysimakhos' time (approximately 280 B.C.) next to the Celsus Library on Curettes Street. The original structure was 2-3 m. below the ground today. The oldest gate to the Agora was on the west side showing Hellenistic features.

The Agora was occupying a large area of 110 x 110 m. in square shape, with a lot of shops surrounding a courtyard except on the north side. Right in front of the shops there was a stoa (a walkway covered with a ceiling and surrounded by columns from the courtyard side). The original Agora had granite columns first, but then during a renovation in the Roman time (approx. 4th century A.D.) they were replaced with the marble columns. The final form of the Agora was set during Emperor Caracalla (211-217).

The most spectacular section of the Agora was the gate made by two freed slaves of Emperor Augustus. These slaves were two men named Mazeus and Mithridates, they built this gate with three passages and dedicated it to the emperor, his wife, daughter and son-in-law. There are inscriptions written in Latin and Hellenistic languages on the top section of the arched gate-ways indicating the builders and the emperors' family to whom the gate was dedicated. This gate opens to the southeast direction, the Harbour side and the Serapis temple direction.

There were also a sun and water clock in the middle of the courtyard. The restoration of this Agora has not started yet.

Agora was built in the third century B.C in the Hellenistic Period, but the ruins date from the reign of Caracalla (211-217 C.E).