The gate with three passage ways at the right of the Celsus Library was built in 40 A.D by the slaves Mazeus and Mythridates for their emperor, Augustus, who gave them their freedom.

The passages are vaulted, the front side of the vault facing the Celsus Library is made of black marble, while the other side is white. A Latin inscription with inlaid letters made of bronze is still visible on one side of the structure. Part of the inscription states: "From the Emperor Caesar Augustus, the son of the god, the greatest of the priests, who was consul twelve and tribune twenty times; and the wife of August Livia; the son of Lucus, Marc Agrippa who was consul three times, Emperor, and tribune six times; and the daughter of Julio Caesar Augustus, Mazeus and Mythridates to their master and the people."

The small area in front of the gate was used as an auditorium. The steps around the gate, in front of the library and the round pedestal were used as seats. In Byzantine Period, the walls in the small area were built when the city walls were reduced in length.