Dasht-e Kavir ( in classical Persian, from khwar (low), and dasht (plain, flatland)), also known as Kavir-e Namak () and the Great Salt Desert, is a large desert lying in the middle of the Iranian Plateau. It is about long by wide with a total surface area of about , making it the world's 24th largest desert. The area of this desert stretches from the Alborz mountain range in the north-west to the Dasht-e Lut in the south-east. It is partitioned among the Iranian provinces of Khorasan, Semnan, Tehran, Isfahan and Yazd. Features In the center of the desert lies the Kavir Buzurg (Great Kavir), which is about 320 km long and wide. In the western part of the desert lies the Daryahcheh-e Namak ("salt lake"), . It contains some large salt plates in a mosaic-like shape. It is part of a protected ecological zone, the Kavir National Park. One of the most desolate parts of Dasht-e Kavir is the Rig-e Jenn (‘Dune of the Jinn’). Climate and structure Dasht-e Kavir's has an arid climate with little precipitation. However, there is usually some rainfall in winter, as well as the mountains that surround it, provide plenty of runoff—enough to create vast seasonal lakes, marshlands and playas. Daytime and nighttime temperatures can vary by as much as over the course of a year. The weather can get quite cold during the nighttime in winter, routinely dropping to below in some areas. Rain usually falls in winter. Usually more elevated areas in Dasht e Kavir have a cold desert climate (BWk) while less elevated areas have a hot desert climate (BWh). The desert soil is covered with sand and pebbles; there are marshes, seasonal lakes and seasonal river beds. The high temperatures and low humidity cause extreme vaporization, which leaves the marshes and mud grounds with large crusts of salt. Heavy storms frequently occur and they can cause sand hills reaching up to 40 m in height. Some parts of Dasht-e Kavir have a more steppe-like appearance. Post-Glacial lake system Almost 3,000 years ago, at the start of the post-glacial era, the Kavir was a series of vast lakes: the Asian monsoon reached deep into central Iran, bringing heavy summer rain that formed numerous lakes in the closed basins of the central Iranian Plateau that today comprises the Kavir and other deserts in the area. There are inscriptions at teppeh Sialk noting