According to Procopius, this period was distinguished by the renewal and foundation of towns (530-552): "Having observed that the ramparts of Serdica and Naissus had been ruined in time... (Justinian) fortified them and made them impregnable to any enemy". He rebuilt 32 fortresses (castles) in the vicinity of Niš:

Calventia, Pharanores, Stranbasta, Aldanes, Barachtestes, Sarmates, Arsena, Brarcedum, Eraria, Bercadium, Sabiniribes, Timiana, Candilar, Arsatsa, Viculea, Castellium, Groffes, Garces, Pistes, Dusmanes, Vratzista, Olodoris, Cassia, Grandetum, Urbriana, Nogeto, Gurbicum, Lautzones, Duliares, Mediana, Tiuncona, Castellium;

He also renovated seven fortresses:

Ad Herculem, Mutziani Castellum, Burdopes, Calis, Millareca, Dedbera, Hesdupara.