The famous Rotunda of Thessaloniki, Macedonia: The Rotunda is one of the most important Roman monuments in Thessaloniki. It stands just next to the Arch of Galerius in the city center and it is also known as the Church of Agios Georgios. This cylindrical structure was built in 306 AD by the Roman tetrarch Galerius, who intended it to be his grave. At first, it worked as a temple but it remains unknown to which god this temple was dedicated.

Eventually, Galerius died in 311 AD and he was buried in Felix Romuliana, modern Serbia. In the 4th century AD, the Byzantine emperor Constantine I converted it into an Orthodox church and many frescoes were painted inside, some of which survive today on the walls of Rotunda .

In the 14th century, the Ottomans occupied Thessaloniki and in 1590, the Rotunda was converted into a mosque. In fact, a minaret was added to the building that has been restored and survives till today. In 1912, the Greeks deliberated Thessaloniki and Rotunda was converted into an Orthodox church again, till 1979, when a strong earthquake caused serious damage to the structure. Presently, the Rotunda has been restored and works as a sculpture museum. Also, it frequently hosts various exhibitions.

The Rotunda has a diameter of 24,5 meters and its walls are more than 6 meters thick, which has protected the monument from time, sieges and earthquakes. This is one of the oldest Orthodox churches and has been included in the UNESCO list of the World Heritage Sites. In fact, all Paleochristian and Byzantine monuments of Thessaloniki were included in this list in 1988.