Ostrvica

Ostrvica, also known as Ostrovica or Sivrice Hisar, was a small fortified town situated on a rocky peak of Rudnik Mountain in central Serbia, approximately four kilometers northwest of the modern town of Rudnik. Constructed before 1323, this military installation served as the primary castle in the region and functioned as a critical component of a defensive system designed to protect the valuable mines of Rudnik. While Ostrvica guarded the northern approaches, it maintained visual signal communication with another fortress to the south, known as Pavle Orlović's Tower, ensuring comprehensive security for the mining operations during the medieval period.

Throughout the 14th and 15th centuries, the castle held significant strategic importance, passing through the control of the Kingdom of Serbia, the Serbian Empire, Moravian Serbia, the Serbian Despotate, and eventually the Ottoman Empire. It frequently served as a refuge for local inhabitants and merchants from Dubrovnik during times of conflict, including the wars between Stefan Dečanski and Stephen Vladislav II. Notable historical figures associated with the site include Nikola Zojić, who governed the fortress in 1398, and Voivode Mazarek in 1414. The stronghold remained active until 1451, when Ottoman forces completely razed the structure to the ground, ending its military utility.

Today, Ostrvica exists only as ruined remnants atop its mountainous location. Although the physical structure was demolished over five centuries ago, its archaeological remains stand as a testament to the region's turbulent medieval history and the extensive network of fortifications that once protected Serbia's economic assets. The site offers insight into the defensive strategies of the era, highlighting how geography and architecture were combined to safeguard vital resources like the Rudnik mines against invading armies and internal strife.