When the waters are high, a rare natural phenomenon can be observed near the village of Bač. The Lan Lake (Laneno jezero in Slovene) overflows and its waters drop into the Bač lake below. Intermittent lakes are a major attraction of the Upper Pivka Valley. From here all the up way to Postojna, a series of lakes dot the landscape. Orchids and other rare plants grow on the lush wet meadows, birds hide in the tall grass and butterflies flutter from flower to flower.