Karakalpakstan, officially the Republic of Karakalpakstan, is an autonomous republic of Uzbekistan. It occupies the whole northwestern part of Uzbekistan. The capital is Nukus (Nókis / Нөкис). The Republic of Karakalpakstan has an area of , and a population of about two million. Its territory covers the classical land of Khwarezm, which in classical Persian literature was known as Kāt (کات). From about 500 BC to 500 AD, the region of what is now Karakalpakstan was a thriving agricultural area supported by extensive irrigation. It was strategically important territory and fiercely contested, as is seen by the more than 50 Khorezm Fortresses which were constructed here. The Karakalpak people, who used to be nomadic herders and fishers, were first recorded by foreigners in the 16th century. Karakalpakstan was ceded to the Russian Empire by the Khanate of Khiva in 1873. Under Soviet rule, it was an autonomous area within the Russian Soviet Federative Socialist Republic before becoming part of Uzbekistan in 1936 as the Karakalpak ASSR. The region was probably at its most prosperous in the 1960s and 1970s, when irrigation from the Amu Darya was being expanded. However, the evaporation of the Aral Sea has made Karakalpakstan one of Uzbekistan's poorest regions. The region is suffering from extensive drought, partly due to climate patterns, but also largely because the Amu Darya and Syr Darya rivers are mostly diverted in the eastern parts of Uzbekistan. Crop failures have deprived about 48,000 people of their main source of income and shortages of potable water have created a surge of infectious diseases. Karakalpakstan is now mostly desert and is located in western Uzbekistan near the Aral Sea, in the lowest part of the Amu Darya basin. It has an area of 164,900 km2 and is surrounded by desert. The Kyzyl Kum Desert is located to the east and the Karakum Desert is located to the south. A rocky plateau extends west to the Caspian Sea.