Underground aqueduct converted into a town

The Kish Qanat in Kariz, Iran is more than 2,500 years old and currently has been converted into an underground town at a depth of 16 meters below the surface, with an area of more than 10,000 sq m. The Qanat is an ancient system found in arid regions that brings groundwater from the mountains, following a water-bearing formation (aquifer), and emerge at an oasis, through a series of tunnels. The tunnels perhaps several kilometers long, are roughly horizontal, with a slope. This allows water to drain out to the surface by gravity to lower and flatter agricultural land. Considered to be the oldest feat of human engineering, this system can be found still working in Iran.