Karst features such as small swallow holes, estavelles, and, to a lesser extent, an outcrop of carbonate rock are also present.

The river meanders through the floodplain at Mirna Peč and disappears beneath the surface in the swallow holes at Goriška Vas.

[8] Due to seasonal flooding in spring and autumn, fertile alluvial soil along the river bank is spread across the valley.

Caves on the slopes of surrounding hillsides give evidence of an ancient outflow; however, at present water supply is limited to groundwater aquifers.

[12] Due to varied species of wild fauna and flora as well as natural habitat types, Koprivnica Hill, the Ajdovec Plateau, and Sluga Cave (Slovene: Slugova jama) are listed as areas protected under the Natura 2000 Act.