It was represented by the King of Cappadocia Ariarathes in the middle of 2nd century B.C. This 12 meter wide and 116 meter long building situated on the north of the agora and West Gate Street.
A 6-stepped stairway in the front opening onto the street leads to wide gallery open to the sky. This gallery is 6.47 meters wide and had a marble paved floor. There were benches on the east and the west side of the gallery of which one was exedra (a room in a public building furnished with seats.) and the other in a horseshoe shape. The certain names from among the people of Priene were mentioned as inscriptions on the back of the seats.
The building is separated into two parts by columns. The wooden roof was supported by 49 Doric columns in the front row and 24 Ionic ones in the second row. There are fifteen rooms at the rear part; three of these are excellent stone workmanship of exedra design. R-The ninth room from the west was consecrated to the cult of Roman gods and Emperor Augustus which is understood from the inscriptions and drawings on the wall of this room. It is also understood that the Julian (Roman) calendar was begun to be used in west Anatolia in the year 9 B.C. It is believed that these rooms were used for the conversations of the State and the Athena Temple archives.