High Quality Content by WIKIPEDIA articles! Greater Khorasan is a modern term for a historical geographic region spanning north-eastern and east of Iran, Turkmenistan, Uzbekistan, Tajikistan, western and northern Afghanistan. The name "Khorasan" is said to derive from Middle Persian khor "sun" ) ayan "out of," hence meaning "land where the sun rises." For other suggested etymologies, see Khwarezm. First established as a political entity by the Sassanids in the 3rd century, the borders of the region have varied considerably during its 1600-year history. It acquired its greatest extent under the Caliphs, for whom "Khorasan" was the name of one of the three political zones under their dominion.