 The largest islands are Cres and Krk, each of them having an area of around .The hilly northern parts of Hrvatsko Zagorje and the flat plains of Slavonia in the east which is part of the Pannonian Basin are traversed by major rivers such as Danube, Drava, Kupa, and Sava.The Danube, Europe's second longest river, runs through the city of Vukovar in the extreme east and forms part of the border with Vojvodina.