Ostrogothic castle on conquered Byzantine castle in the 6th century

The Huns advancing from Central Asia drove the Visigoths and Ostrogoths from their settlement areas to the west and south across the Balkans and forced them to invade the Byzantine Empire.
The castle “Golemanovo Kale near Sadovets in the Vit Valley in Bulgaria” is one of a series of fortifications in the Balkans that were primarily built in the 6th century by the Ostrogoths, perhaps in part on the remains of abandoned or conquered Byzantine castles.