The flow of the river can be divided into upper, middle and lower course. As Croatia is a small country, large European rivers such as Drava and Danube flow within its administrative boundaries only in middle or lower part of their course. One of the rare examples of the river with its entire stream flowing through Croatia is the river Kupa. The upper course is characterized by rapids over which the river breaks through the canyon. By erosion in the mountainous or karst areas the river carves canyons or creates valleys.