Longest Underground Aquifer in the World Discovered

Roman engineers spent a century digging an underground aqueduct through 66 miles of stone in order to bring water to Syria. The previous longest underground water aqueduct was in Bologna; it was only 12 miles long.

The soldiers chiseled over 600,000 cubic meters of stone from the ground -- or the equivalent of one-quarter of the Great Pyramid of Cheops.

"Over the first 60 kilometers, the tunnel has a gradient of 0.3 per thousand," explains the project director. That works out to 30 centimeters per kilometer -- an astonishingly shallow angle of descent. LINK

Link - Via: britannica