Kras (German: Karst; Italian: Carso), also known as the Classical Karst or the Kras Plateau, is a limestone borerline plateau region in southwestern Slovenia extending into northeastern Italy. It lies between the Vipava Valley, the low hills surrunding the valley, the westernmost part of the Brkini Hills, and the Gulf of Trieste. Its western edge is also the traditional ethnic border between Italians and Slovenes. The region is famous as the inspiration for the geological term karst topography.