http://agathe.gr/guide/odeion_of_agrippa.html
Odeion of Agrippa Late in the 1st century B.C. the Athenians were given money for a new marketplace by Caesar and Augustus, and the northern half of the old Agora square was filled with two new structures, ... Odeion of Agrippa Late in the 1st century B.C. the Athenians were given money for a new marketplace by Caesar and Augustus, and the northern half of the old Agora square was filled with two new structures, the Odeion of Agrippa and the Temple of Ares. ... The structure was rebuilt as a lecture hall, with the seating capacity reduced to about 500, and a far more elaborate facade was built at the north, using massive pillars carved in the form of giants (snaky tales) and tritons (fishy tails) (Fig. 54). ... It was rebuilt in the early 5th century A.D. as part of a sprawling complex, perhaps a palace, with numerous rooms, a bath, and several courtyards, which extended southward all the way across the old South Square (Fig. 55).