NIS The ancient Roman town of Naissus, present-day Nis, was an important frontier fortress of the Roman Empire. It was here that the Emperor Constantine was born. A superb bronze head of the Emperor, discovered in Nis, is now in the National Museum in Belgrade. The remains of a Roman summer resort, Mediana, with the foundations of villas, mosaics and marble figures, have been unearthed in the vicinity of Nis. A 6th century Byzantine tomb, discovered in the city, includes well-preserved frescoes with zoomorphic and floral motifs.