Unesco-listed Felix Romuliana was built for the Roman emperor Galerius and completed around AD 313. Ravaged by the Huns in the 5th century and abandoned following the arrival of the Slavs, who named it Gamzigrad ('Slither Town'), today the palace lies in ruins. Most archaeological findings from the site, including a bust of Galerius, are kept in Zaječar's National Museum. Still, the sprawling grassy mounds and the remains of massive ramparts, gates, towers and Corynthian pillars are impressive.
The palace had two temples, a 4th-century Christian basilica, public baths and mausoleums where Galerius and his mother Romula were buried. The most interesting surviving floor mosaics are the ones depicting the Labyrinth and god of wine Dionysus; they can be seen in the Zaječar museum.
Gamzigrad is 11km west of Zaječar in eastern Serbia. Local buses from Zaječar run to Gamzigrad every hour, or it's a 15-minute taxi ride from town. Buses run from Belgrade to Zaječar (1400RSD, four hours, 10 daily).