North Macedonia is a landlocked country that is geographically clearly defined by a central valley formed by the Vardar river and framed along its borders by mountain ranges. The terrain is mostly rugged, located between the Šar Mountains and Osogovo, which frame the valley of the Vardar river. Three large lakes—Lake Ohrid, Lake Prespa and Dojran Lake—lie on the southern borders, bisected by the frontiers with Albania and Greece. Ohrid is considered to be one of the oldest lakes and biotopes in the world. The region is seismically active and has been the site of destructive earthquakes in the past, most recently in 1963 when Skopje was heavily damaged by a major earthquake, killing over 1,000.