The river Bistrica cut the most of its channel through the triassic rocks and some vast pebble deposits show us its torrential character. It is known by its diversity, clear waters and sudden changes of wider and narrower areas in the valley. The canyon between Trebče and Zagaj is so tight that it is impassable. The channel is surrounded by steep, rocky and wooded areas. But the nature in the canyon is very lively. It is home to some less famous and endangered vegetable species. The basin of the Bistrica is also home to trouts and river crabs.