Merv is advantageously situated in the inland delta of the Murghab River, which flows from its source in the Hindu Kush northwards through the Garagum desert. The Murghab delta region, known to the Greeks as Margiana, gives Merv two distinct advantages: first, it provides an easy southeast-northwest route from the Afghan highlands towards the lowlands of Karakum, the Amu Darya valley and Khwarezm. Second, the Murgab delta, being a large well-watered zone in the midst of the dry Karakum, serves as a natural stopping-point for the routes from northwest Iran towards Transoxiana - the Silk Roads. The delta, and thus Merv, lies at the junction of these two routes: the northwest-southeast route to Herat and Balkh (to the Indus and beyond) and the southwest-northeast route from Tus and Nishapur to Bukhara and Samarkand.