This imposing brick construction built right on the junction of Apostolou Pavlou Street and Filippou Street has had many different uses during its long history throughout the centuries. It is commonly known among locals as Rotunda because of its circular ground plan, probably built during the reign of Galerius Caesar (306-311A.D.). It is a characteristic specimen of monumental architecture of the Late Roman period but we don’t really know what it was initially built for. Historians and archaeologists have been arguing for over 50 years about whether it used to be a Pantheon or a Temple dedicated to Zeus or even the funerary monument of the Emperor Galerius himself. What we do know is the history of the Christian period of the monument. This construction, like many others at the time, was converted into a Christian church during the reign of Emperor Theodosius the First, and it was dedicated to the Pantocrator (or according to another source to the Agioi Asomatoi). During the same period the huge dome (diameter 24m.) and the vaults of the three recesses were decorated with elaborate mosaics. The iconographic patterns of the church were very complicated but are more or less known to us. At the top of the dome you could see the Pantocrator surrounded by angels and in the lower section (which is preserved in better condition) there were lines of Saints with a repetitive architectural background behind them. The main theme was the second coming of Jesus. During the Mid-byzantine period it became the town cathedral and in 1591 it was turned into a mosque by the Ottomans. Except for Rotunda, this temple is also known as Agios Georgios (Saint George) taking its name from the adjoining chapel. Today it functions as an exhibition space, hosting various activities of cultural character.