The Stoa, on the east side of the Ancient Agora, was the gift of Attalos II, King of Pergamon, as a fragmentary inscription on the epistyle of its lower colonnade shows: «King Attalos, son of Attalos and of Queen Apollonis». The stoa is identified as a gift to the city of Athens for the education that Attalos received there. A dedicatory inscription on the architrave is engraved as built by Attalos II ruler of Pergamon from 159 BC to 138 BC.
The building is 120 m wide and 20 m deep and had two floors with a second series of columns on the interior and 21 shops at the back of both floors. On the ground floor the exterior colonnade was Doric and the interior Ionic, without fluting. On the upper floor the exterior colonnade was Ionic, and the interior had capitals of a Pergamene type.
The building is similar in its basic design to the Stoa that Attalos’ brother, and predecessor as king, Eumenes II had erected on the south slope of the Acropolis next to the theatre of Dionysus. The main difference is that Attalos’ stoa had a row of rooms at the rear on the ground floor that have been interpreted as shops.
The Stoa of Attalos was a place for Athenians to meet, walk, and to do business. It was destroyed by the Heruli in A.D. 267, and its members were incorporated into the Late Roman Wall. The ruins became part of a fortification wall, which made it easily seen in modern times. In the 1950s, the Stoa of Attalos was fully reconstructed and the Ancient Agora Museum was created by the American School of Classical Studies at Athens, with funding donated by the Rockefeller family.
The Stoa of Attalos houses the Museum of the Ancient Agora. Its exhibits are mostly connected with the Athenian democracy. The collection of the museum includes clay, bronze and glass objects, sculptures, coins and inscriptions from the 7th to the 5th century BC, as well as pottery of the Byzantine period and the Turkish conquest.