The always interesting Smithsonian Past Imperfect blog offers up a nice little D&D-ish story of ancient myth and amateur archeology:
But only when the men went deeper into the hillside did the greatest mystery of the tunnels revealed itself. There, hidden at the bottom of a much steeper passage, and behind a second S-bend that prevented anyone approaching from seeing it until the final moment, ran an underground stream. A small “landing stage” projected out into the sulfurous waters, which ran from left to right across the tunnel and disappeared into the darkness. And the river itself was hot to the touch–in places it approached boiling point.