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