Montenegro is a south-eastern European country, with Podgorica as its capital and largest city. The former royal capital and cultural center of Montenegro, Cetinje is home to a number of national institutions, among them the official residence of the President of Montenegro. Along Montenegro's borders with Serbia, Kosovo and Albania are high mountain peaks, a segment of the Karst of the western Balkan Peninsula and a narrow coastal plain just 1.5 to 6 km wide. Montenegro's extensive karst landscape is generally at an altitude of 1,000 meters above sea level, but parts of it rise to 2,000 meters, such as Mount Orjen, which is the highest massif of the coastal limestone mountains. The lowest section is the Zeta River valley, at 500 meters altitude. Montenegro's mountains are some of Europe's most rugged, with an average altitude of over 2000 meters. The Bobotov Kuk in the Durmitor Mountains is one of the country's most famous peaks, reaching an altitude of 2 522 meters. Its geological base, landscape, climate and soil diversity, as well as its location on the Balkan Peninsula and the Adriatic Sea, have created conditions for high biodiversity, making Montenegro a biodiversity hotspot in Europe and the world. According to biological estimates, Montenegro is home to more than 1200 freshwater algae species, 300 marine algae species, 589 moss species, 7000-8000 vascular plant species, 2000 fungi species, 16000-20000 insect species, 407 marine fish species, 56 reptile species, 333 species of birds that are regular visitors and a high diversity of mammals.