The palace complex of Galerius Maximianus was built in ca. 300 A. D. to become the administrative and religious center of Roman Thessaloniki. The Rotonda, the Arch of Galerius, the Palace, the Octagon and the Hippodrome are its main buildings. The southeast part of the complex is still visible. It comprises large corridors, paved with mosaics and marble slabs around a central atrium with colonnade that is surrounded by rectangular rooms. Along the east corridor four arched rooms are situated next to a large ceremonial hall with niche and mosaic floor. A monumental passage on the south led to the harbor. Founded on the spot of an older rectangular hall the Octagon is a monumental building, possibly a throne-hall, richly decorated with colorful marble slabs and paving.