Sisak ( ; ; also known by other alternative names ) is a city and episcopal see in central Croatia, located at the confluence of the Kupa, Sava and Odra rivers, 57 kilometers southeast of the Croatian capital Zagreb, and is usually considered to be where the Posavina (Sava basin) begins, with an elevation of 99 m. The city's total population in 2011 was 47,768 of which 33,322 live in the urban settlement (naselje).