There is no other city –apart from Constantinople- in the eastern Mediterranean so rich in Christian monuments as Thessaloniki. The city of Saint Dimitrios is full of monuments that began being built during the 4th century and from there and on each era left its own mark in the passage of time. Up to the years of the Ottomanic domination there are buildings and monuments which have outstanding architectural form, sculptures for decoration and very rich and of fine quality murals as well as mosaic work. Apart from the cultural and financial development, Thessaloniki was the second biggest city in the entire Byzantine era and center of Christianity in the eastern world and the Balkans, partially because of the artistic value of the monuments. From this city, artists transferred the knowledge, the technique and the innovative forms to every territory of the Empire. Rotonda, or else Saint George, is one of the most important monuments in the city. It was the south section of the palace that Galerius Ceasar built round 300 AC. This circular-shaped and of impressive size monument was connected to the main palace through a huge hallway, the Galerius Arch. Up to today the archeologists haven’t agreed on the purpose this building was supposed to serve. Some say that it was meant to be Galerius’ final resting place, but it’s known that he died and was buried away from Thessaloniki. Others say that it was a temple dedicated to Kavirus, or even to Zeus. The point of view which is most possible is the one that says that it was used for formal ceremonies and meetings with ambassadors. In 379- 375 when great Theodosios was on the throne of the Empire, Rotonda became a Christian temple, yet un-known dedicated to whom. Much later it was renamed to Saint George, taking the name after the small temple standing on the west side across the gate. It seems almost untrue and is of the peculiar facts in the course of hi-story that such a gigantic building took its name from a small temple which stands in the shadows. During the ages of the Ottomanic domination (1590) Rotonda became a Muslim temple. In 1912, after the liberation it became a Christian temple again and since 1920 it is used as a museum and that hosts Christian sculptures and cultural events. From the period of the early Christian ages the sculpture that represents the three Magicians bringing their gifts to baby Christ is saved and is nowadays kept at the Constantinople Museum. The outstanding mosaic work combines the early Christian ages character and the post Roman technique in a world that the visible and the invisible co- exist. The colors are vivid. The building is 29,8 meters high, the diameter is 24,5 meters an the walls are 6,3 meters thick. It was made of stone.