Fecha en Lancaster 2015 fig 57

3. Rotunda
Plateia Agiou Georgiou Rotonta
306; conversion to church – late 4th century

https://grandeflanerie.com/portfolio/byzantinethessaloniki/

The Rotunda stands northeast of the Arch of Galerius. It was built by Galerius, either as his mausoleum or as a temple dedicated to Zeus or the Cabeiri, a group of chthonic deities.

The Rotunda is a huge building, with a diameter of 24.5 m and height of 29.8 m. Its walls are more than 6 m thick and made of rubble masonry, with wide zones of brickwork appearing at intervals. That is why the building has survived the numerous earthquakes of Thessaloniki. A flat dome covers the structure. It originally had an oculus, like the Pantheon in Rome.