Cerkniako jezero z okolico (Lake Cerknica and its environs). 19/01/06; 7,250 ha, 45°45'N 014°23'E. Natura 2000 site, Ecologically Important Area, Regional Park. The largest and most typical intermittent karst lake in its region. It is formed during rainy periods when the volume of water can no longer be drained through sinkholes, and the lake has no surface outflow, discharging exclusively underground. Numerous picturesque karst phenomena, such as karst sources, estavelles, ponors and ponor caves, abound, and the Kri~na cave is renowned for its underground lakes; the Rakov `kocjan valley, formed by the collapse of ceilings of underground caves, and the River Rak are fed mainly by water from the lake. These special habitats support many rare and endemic species, such as cave beetle and cave salamander, and the lake is the only nesting site in Slovenia for the red-necked grebe, the redshank and the ferruginous duck as well as a breeding place for the corncrake. Remains of Palaeolithic, Mesolithic, and Iron Age settlements are found on Gorica Island in the middle of the lake, as well as prehistoric settlements from the 12th to the 4th centuries BC and a Roman necropolis nearby. Frequent, unpredictable flooding makes intensive agriculture impossible, but pasture and forest uses are widespread, besides some small recreation grounds; appropriate tourist facilities are needed to avoid adverse effects of unorganised tourism. Ramsar site no. 1600. Most recent RIS information: 2006.