The Karst Plateau or the Karst region (, ), also locally called Karst, is a karst plateau region extending across the border of southwestern Slovenia and northeastern Italy. It lies between the Vipava Valley, the low hills surrounding the valley, the westernmost part of the Brkini Hills, northern Istria, and the Gulf of Trieste. The western edge of the plateau also marks the traditional ethnic border between Italians and Slovenes. The region gave its name to karst topography. For this reason, it is also referred to as the Classical Karst. Geographical position The plateau rises quite steeply above the neighboring landscape, except for its northeastern side, where the steepness is less pronounced. The plateau gradually descends from the southeast to the southwest. On average it lies 334 m above sea level. Its western edge, known as the Karst Rim (), is a continuation of the Učka mountain range in eastern Istria, and rises to the east and southeast of Trieste, ending in steep cliffs between Aurisina and Duino. Many interesting geological phenomena occur along the Karst Rim, including the picturesque Rosandra Valley (also known as Glinščica). Because the Karst steeply descends towards the Adriatic Sea, it is less exposed to the beneficial climatological effects of the Mediterranean. In the past, the main vegetation on the plateau was oaks, but these were replaced by pine forests in the 19th and 20th centuries. Forests now cover only one third of the Karst. Starting in the Middle Ages, the plateau suffered radical deforestation for economic reasons. Although it is often said that much of the wood for the closely spaced piles that support the island city of Venice, this is unlikely. Venice perhaps used the wood for naval timber. The most radical deforestation occurred in the first half of the nineteenth century due to clear-cutting by local farmers and conversion of the land into pastures for goats and sheep. The Karst is famous for its caves. In Slovenia, they include Vilenica Cave (the oldest show cave in Europe), Lipica Cave, Divača Cave, Kačna Cave, Postojna Cave, and Škocjan Caves (a UNESCO World Heritage Site), and Grotta Gigante in Italy (the largest show cave in the world). Most of the Karst is located in the Slovenian Littoral, covering an area of 429 square kilometres, with a population of about 19,000 people. The Karst as a whole has exactly 100 settlements. The town of Sežana