The river Krka, the longest entirely Slovenian river, rises in a broad blind valley north of the village of Krka. Its waters come to the surface at the Pod jamo spring.
In its upper course it is strengthened by smaller karst tributaries, and otherwise the waters of the wide karst hinterland of the Grosuplje basin and Velike Lašče flow underground towards it. Since its water is saturated with limestone, in its upper course this is deposited as tufa and forms characteristic barriers and thresholds.
Beside them numerous mills and sawmills once operated, but today they have only a recreational and tourist role.
With 7 terrestrial and 31 aquatic species of cave animals, the underground system of the river Krka is among the 20 richest in the world.