Okay, that's %$*%&(^@& impressive!

The Ancient World's Longest Underground Aqueduct:

Roman engineers chipped an aqueduct through more than 100 kilometers of stone to connect water to cities in the ancient province of Syria. The monumental effort took more than a century, says the German researcher who discovered it.

Seriously, read this article. It's one of those "blows your mind beyond all comprehension" that the Romans could do so much [without a compass, for example! -ed] It does spoil the romance (at the expense of the realism) to learn at the end that this massive underground aqueduct turns out to have been a white elephant: it didn't do what it was intended to do, having been out a fractional degree for 90-some kilometres. Still kind of surprising the Romans couldn't have figured something out.