Beneath Iran's Dusty Desert Lie Ancient Water Tunnels Still in Use | National Geographic
Thousands of years ago, Persians created an ingenious system to provide water across their arid landscape. They tapped aquifers at the heads of valleys and designed tunnels that utilized gravity to send the water to settlements. It's now estimated that the combined length of all the underground channels, known as qanats, in Iran is equivalent to the distance between the Earth and the Moon.
