Montenegro (; lit. "Black Mountain") is a small, mountainous state in south-west Balkans. Montenegro borders Croatia, Bosnia and Herzegovina, Serbia, Albania, Kosovo and the Adriatic Sea. While being a small country at 13,812 km2 (5,332 sq mi), it is very diverse regarding the terrain configuration. Montenegro has 50 peaks of over 2,000m in altitude. Terrain Terrain in Montenegro ranges from high mountains in the northern part of the country, through karst segment in central and western part, to almost 300 km of a narrow coastal plain. The coastal plain disappears completely in the north, where Mount Lovćen and other mountain ranges plunge abruptly into the inlet of the Gulf of Kotor. The coastal region is noted for active seismicity. Montenegro's section of the karst lies generally at elevations of above sea level-although some areas rise to . The lowest segment is in the valley of the Zeta River, which flows at an elevation ranging from to . The river occupies the centre of Nikšić field, a flat-floored, elongated depression typical of karstic regions. The underlying rock is predominantly limestone, which dissolves to form sinkholes and caves. The longest cave in Montenegro is Vražji firovi - 10,5 km long cave north-east from Berane, and the deepest sinkhole is Željezna jama -1027 m on mount Maganik. The Zeta River Valley, or Bjelopavlići plain, merges in the southeast with the second significant flat lowland in Montenegro, the Zeta plain. Zeta plain stretches north of the Lake Scutari at elevation of . The two plains are today the most densely populated areas of Montenegro, housing the two biggest Montenegrin cities, Podgorica and Nikšić. The high mountains of Montenegro include some of the most rugged terrain in Europe. They average more than in elevation. Among notable peaks is Bobotov Kuk in the Durmitor mountain, which reaches . The Montenegrin mountains were the most ice-eroded section of the Balkan Peninsula during the last glacial period. The Coast The coast of Montenegro is long. Unlike its northern neighbour Croatia, Montenegro has no large inhabited islands along the coast. A notable feature of the Montenegrin coast is Bay of Kotor, a fjord-like gulf, which is in fact a submerged river canyon. The Bay of Kotor is surrounded by mountains up to high, which plunge almost vertically into the sea. To the south of the Bay of Kotor, there is a narrow coastal plain, no more than 4 km