The island of Golem Grad is located in Prespa Lake, on the border with Albania and Greece. It represents a natural fortress, 30 m above the lake surface, with an area of 18 ha. The systematic excavations, which started in 1967/68, continued from 1980 until 1990 and from 1999 until 2006.

The site represents settlement from the Neolithic period and Hellenistic and Roman times. The cemeteries dating to the classical, late-antique and mediaeval periods were also discovered. Only a few stone artifacts date from the Neolithic period. Two partially discovered houses belong to the Hellenistic period, and houses and one cistern, which was transformed later (during the Middle Ages) into a church, are dated to Roman times. The foundations of two one-aisled early Christian basilicas were discovered, and foundations are preserved of the church from the 14th century dedicated to St. Demetrius. The church of St. Peter, also from the 14th century, has partially preserved frescoes inside. On the southern wall on the outside, a rear representation in fresco of the siege of Constantinople is preserved. In the cemeteries that date from the 5th-4th centuries BC and continuously from the 2nd until the 14th century AD, attractive jewellery made of bronze, amber, glass, silver and gold was discovered.

During the research, campaign in 2000 excavations was carried out on several locations: at the mediaeval necropolis around church St. Demetrius, at the cistern and roman house.