Qanats in Iran, subterranean aqueducts, horizontal wells. Undoubtedly a technique invented in the Iranian highlands, probably in Achaemenian times (or even earlier), and exported over centuries to other countries in the same predicament and similar topographical predisposition - waterless desert ringed with sizable mountains. Some qanat shafts in Iran are alleged to reach down to depths of 400 m; one qanat is 60 km long. The image shows qanats near Yazd, (Fars Province, IRAN).