The Kish Qanat is an amazing feet of human engineering that covers over 10,000 square metres underground. The tunnel complex, built before the Roman Empire, serves as a way to transport water from Iran's mountain region to less arid land several kilometres away.
The ancient water provision technology can be described as the greatest contribution made by Iranians to hydraulics. This system must have been started at least 5000 years ago in Iran. The water from the qanat flowed in a natural underground stream between a layer of corals on the surface of the island. The drinking water flowed from northeast of the Island to the sea and after 10 centuries it continues to flow.
http://coolthingsinrandomplaces.com/underground-town-of-kariz-iran/#more-131
From the Upcoming ueue, submitted by coconutnut.
[Thanks to Monty Python!]
"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."
Wouldn't transporting water to "more arid land" make more sense?
-Andrew