Ostrvica or Ostrovica hill (758 m, ) is located on the northwest of the Rudnik massif, sharply rising above the surrounding terrain. It is of volcanic origin and made of magmatic rocks, chiefly andesite, suitable for masonry and road building. On the top of the hill lie the remains of a fortified city, whose exact origins are unknown. It was first mentioned in the fifth century CE, but is presumed to originate from the antic period. It was refortified by Serbian Despot Đurađ Branković around 1430, who used it as a summer retreat with his family. The popular legend attributed the city building to his wife Eirene Kantakouzene, already infamous for her role in building of the Smederevo Fortress, and it is also referred to as Jerinin grad (Eirene's city).