Similar as many other famous Romans (Julius Caesar and Pompey, Brutus, the Emperors Anthony and Octavius etc.), who had stayed in Thessaloniki, Galerius Valerius Maximianus, one of the four co-emperors of the Tetrach of the Roman Empire at the end of the 3rd century and in the beginning of the 4th (297-307), had choosen Thessaloniki as his seat.
Galerius decided to adorn the city, in a true Roman way, with imposing buildings and structures. As a result, along with the Eastern Walls of the city, he created a large palace complex – Galerius Palace – consisting of huge buildings, the palace, the octagon, the Rotunda, a large Hippodrome, arcades, triumphal arches etc.
Where Navarinou Square and Demetriou Gounari Street is now located, a significant part of the Galerius Palace complex has been excavated including massive walls, a large internal courtyard, peristyle, corridors and rooms with beautiful mosaic floors, fountains and springs. On the southwest part of the site is where the Octagon lies, a large octagonal stucture of almost 30m in internal diameter, which was a temple or the throne room with a wonderful floor paving remaining. The Hippodrome (400m in length), lies on the east of the Palace, unfortunately underneath the block of flats in the Hippodrome Square. Many of its remaining marbles and stones were later used in various repairs to the western walls. On a large marble archway found on the site, which is now placed in the Archaelogical Museum of Thessaloniki, two main figures of the city are represented, the embodiment of Thessaloniki and Galerius himself.