Nagorno-Karabakh has a total area of . Approximately half of Nagorno-Karabakh terrain is over above sea level. The borders of Nagorno-Karabakh resemble a kidney bean with the indentation on the east side. It has tall mountain ridges along the northern edge and along the west and mountainous south. The part near the indentation of the kidney bean itself is a relatively flat valley, with the two edges of the bean, the districts of Martakert and Martuni, having flatlands as well. Other flatter valleys exist around the Sarsang reservoir, Hadrut, and the south. The entire region lies, on average, above sea level. Notable peaks include the border mountain Murovdag and the Great Kirs mountain chain in the junction of Shusha and Hadrut districts. The territory of modern Nagorno-Karabakh forms a portion of the historic region of Karabakh, which lies between the rivers Kura and Araxes, and the modern Armenia-Azerbaijan border. Nagorno-Karabakh in its modern borders is part of the larger region of Upper Karabakh.