High Quality Content by WIKIPEDIA articles! Sisak (pronounced ; Slovene: Sisek, Serbian Cyrillic: Сисак, German: Sissek, Hungarian: Sziszek, Latin: Siscia) is a city in central Croatia. The city`s population in 2011 was 33,049, with a total of 49,699 in the administrative region and it is also the administrative centre of the Sisak-Moslavina county. Sisak is located at the confluence of the Kupa, Sava, and Odra rivers, 57 km (35 mi) southeast of the Croatian capital Zagreb.