Qanat

A qanat is a series of well-like holes and tunnels dug to reach a natural underground source of water, usually run-off from a mountain. They were (and are) used to provide water in the desert regions of the Middle East. The oldest qanats, found in the region once known as Persia (now known as Iran), are believed to be a couple of thousand years old.

Cross-section of a Qanat.