Sistān, also known as Sakastān and Sijistan (سِجِستان), is a historical region in south-eastern Iran and extending across the borders of present-day south-western Afghanistan, and south-western Pakistan. Mostly corresponding to the then Achaemenid region of Drangiana and extending southwards of the Helmand River not far off from the city of Alexandria in Arachosia. Largely desert, the region is bisected by the Helmand River, which empties into the Hamun Lake, located in Zabol, that forms part of the border between Iran and Afghanistan.