Khorezm fortresses

The Khorezm Fortresses, or Elliq Qala in Uzbek, are a collection of more than 50 desert fortresses in Karakalpakstan and the Khorezm Region of Uzbekistan. They are included on UNESCO’s Tentative List for World Heritage Site status as the Desert Castles of Ancient Khorezm.
Geography.
The Khorezm Oasis is an area of the Amu Darya river delta in western Central Asia. It is bordered to the north by the Aral Sea, to the east by the Kyzylkum Desert, and the south by the Karakum Desert. To the west is the Ustyurt Plateau. Today, the region is divided between Uzbekistan (including the autonomous Republic of Karakalpakstan) and Turkmenistan.
History.
Khorezm has been occupied by humans since Paleolithic times. The first fortified sites date from the 7th century BC, and the number and size of the fortresses increased from the 6th to  4th centuries BC once Khorezm became a vassal state of the Achaemenid Empire. 
Khorezm became an independent state between the 4th century BC and the 1st century AD. The Greek historian Arrian records that Pharasmenes, king of Khorezm, visited Alexander the Great in Samarkand and offered his assistance in subjugating lands bordering Khorezm. Power struggles in the wake of Alexander’s death destabilised much of Central Asia, and displaced tribes, including the Kushans, moved west. The  Kushans certainly influenced Khorezm, though it is unclear if Khorezm was formally part of their empire.
From the 4th century, Khorezm was subject to multiple attacks, including from the Huns, the Turks, and, later, the Arabs. The Afrighids (305-995) brought some stability, but they continued to fortify Khorezm to protect their territory and overland trade.