High Quality Content by WIKIPEDIA articles! Odra is a river in central Croatia. It is 83 km (52 mi) long and its basin covers an area of 604 km2 (233 sq mi). Its source is in the Zumberak mountain, southwest of Zagreb. It flows eastwards, passes south of Velika Gorica, then turns south-east, more or less parallel to the river Sava. It flows into the river Kupa near Odra Sisačka, just northeast of Sisak, also just before the Kupa joins the river Sava.