Spiegel has an extensive article on Mathias Döring’s efforts to enlighten the world about the Gadara aqueduct which he began following/discovered back in 2004 (I think). Here’s a bit of a tease from the article:
The tunnel was discovered by Mathias Döring, a hydromechanics professor in Darmstadt, Germany. Treading on moss-covered steps, he squeezes his way into dark caverns plastered with waterproof mortar. Greek letters are emblazoned on the walls, and bats dart through the air. “Sometimes we have to stop working — there isn’t enough oxygen,” says the project director.
Qanat Firaun, “Canal of the Pharaohs,” is what the locals call the weathered old pipeline. There are even rumors that gold is hidden in the underground passageways that run up to 80 meters (262 feet) below the surface.
Döring has found a better explanation. It turns out the aqueduct is of Roman origin. It begins in an ancient swamp in Syria, which has long since dried out, and extends for 64 kilometers on the surface before it disappears into three tunnels, with lengths of 1, 11 and 94 kilometers. The longest previously known underground water channel of the antique world — in Bologna — is only 19 kilometers long.
“Amazing” is the word that the researcher uses to describe the achievement of the construction crews, who were most likely legionnaires. 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. This colossal waterworks project supplied the great cities of the “Decapolis” — a league originally consisting of 10 ancient communities — with spring water. The aqueduct ended in Gadara, a city with a population of approximately 50,000. According to the Bible, this is where Jesus exorcized demons and chased them into a herd of pigs.
Folks who can read German might also be interested in the following (pdf) mentioned in the Wikipedia page on the Gadara aqueduct:
Mathias Döring: “Wasser für Gadara. 94 km langer Tunnel antiker Tunnel im Norden Jordaniens entdeckt”, Querschnitt, Vol. 21 (2007), pp. 24–35.