The Rotunda of Thessaloniki is an ancient Roman monument located in Thessaloniki, Greece. Originally built in the early 4th century AD during the reign of Emperor Galerius, it was initially constructed as a mausoleum or temple. The structure is notable for its impressive circular design with a large dome, which was an architectural achievement of its time.

The Rotunda has served multiple purposes throughout its long history—it functioned as a Christian church, a mosque during Ottoman rule, and is now a museum and UNESCO World Heritage Site. Its interior features beautiful Byzantine mosaics and marble decorations, though many have been lost or damaged over the centuries.

The building stands as one of the best-preserved examples of Roman architecture in Greece and remains one of Thessaloniki’s most iconic landmarks. It’s located near Galerius’s Palace and the Arch of Galerius, forming part of an important archaeological complex that reflects the city’s significance during the Roman period.