Also known as Ayios Giorgios, this brickwork edifice has become a layered monument to the city's rich history. Built in AD 306, it was probably intended as Roman emperor Galerius's mausoleum. However, when he died in Bulgaria, his successor refused to have the body brought back. Under Theodosius the Great, the Byzantines converted the Rotunda into a church dedicated to St. George, adding the impressive 4th-century AD mosaics of early saints. The Ottomans made it a mosque (the minaret still stands). It was restored after damage suffered in a 1978 earthquake, and is still undergoing restoration at this writing. Once a month and on major holidays a liturgy is held here, as are occasional art exhibits and concerts.
- Address: Plateia Agiou Georgiou, Kentro, Thessaloniki, 54009
- Phone: 2310/968860
- Hours: May–Oct., 8–3; Nov.–Apr., Tues.–Sun. 8:30–3
- Location: Kentro and Ladadika