Khwarezm, or Chorasmia, is a large oasis region on the Amu Darya river delta in western Central Asia, which borders to the north the (former) Aral Sea, to the east the Kyzylkum desert, to the south the Karakum desert and to the west the Ustyurt Plateau. It was the center of the (indigenous) Khwarezmian civilization and a series of kingdoms, whose capitals were (among others) Kath, Gurganj (the modern Köneürgenç) and, from the 16th century on, Khiva. Today Khwarezm belongs partly to Uzbekistan and partly to Turkmenistan.