Montenegro (Montenegrin: Crna Gora, Црна Гора, meaning "black mountain") is a small, mountainous state in south-west Balkans. Montenegro borders Croatia, Bosnia and Herzegovina, Serbia, Kosovo, Albania 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.
Terrain in Montenegro ranges from high mountains in the northern part of the country, through karst segment in central and western part, to 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 100 m (328 ft) above sea level-although some areas rise to 1,800 m (5,906 ft). The lowest segment is in the valley of the Zeta River, which flows at an elevation of 450 m (1,476 ft). 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 underground caves. The longest cave in Montenegro is Vražji firovi - 17,5 km long cave north-east from Berane, and the deepest sinkhole is Željezna jama -1162 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 40 m (131 ft). The two plains are today the most densely populated areas of Montenegro, housing the two biggest Montenegrin cities, Podgorica and Nikšić.