It was built between 19 and 11 B.C. with a donation of Julius Caesar and Augustus. During the reign of Hadrian the court was paved with slabs. After the invasion of the Herulae in A.D. 267 the city of Athens was restricted to the area within the Late Roman fortification wall, and the administrative and commercial centre of the city was transferred from the Ancient Agora to the Roman Agora and the Library of Hadrian.
During the Byzantine period and the Turkish occupation the area was covered with houses, workshops and churches along with the Fethiye Mosque.
After the necessary purchase and demolition of the private houses and other buildings covering the area, a series of excavations were carried out by the Greek Archaeological Society (in 1837-45, 1890-91, 1920, 1930-31), by the Italians (in 1940-42), by An. Orlandos and P. Lazarides (in 1963-64) and by the 1st Ephorate of Antiquities (in 1955, 1965-66, 1968, 1984-85, 1989, 1991).