It must have been kept fresh by an underground stream, because the water was cold and clear.

NEWYORKER: Wakefield

Now, in this warren of rooms, except for the muffled sound of the crowd above, the only sound was the whooshing of an underground stream, redirected here from Roman times for irrigation and cleaning.

FORBES: Seeing The Colosseum As The Gladiators Did

They are widely regarded as a world-class natural attraction containing marvellous stream passages formed by three rivers that sink underground on the slopes of Cuilcagh Mountain.

UNESCO: Olympic torch carried through iconic Geopark

It's the first such visual record made possible by the University of Minnesota-operated facility that, when completed, will extend for more than 200 feet underground in an area near the Canadian border and endure regular bombardment by a controlled stream of neutrinos.

ENGADGET