or Seistan
Extensive border region, eastern Iran and southwestern Afghanistan.
Most of its sparse population and about two-fifths of its area lie in Iran. It comprises a large marshland depression with a true desert climate. It is the reputed homeland of the legendary Kay 0101; nian dynasty of Persia and played an important part in Persian history, especially under the Safavid dynasty (15021736). In the 19th century it was the centre of a dispute between Persia and Afghanistan that led to the establishment of their modern frontier.