"You can see that the two aqueducts were built side by side," Tassan pointed out. "One fed the water mill just below, the other provided water to Arles. Now we're going to see something unusual." We followed the second aqueduct as it veered sharply to the right, away from the promontory, through an olive grove. Then, abruptly, it disappeared.
"What happened here?" I asked him.
He shrugged. "It could have been destroyed by the barbarians, to cut off the water supply to Arles," he replied. "But that's just a hypothesis. Nobody knows."
Tassan stood pensively beside the last stone arch for a time. Then, he pulled out his tape measure, got back down on his hands and knees, and began examining one more set of chariot-wheel grooves on the ancient road.
Writer Joshua Hammer is based in Berlin.
Photographer Clay McLachlan works from Paris.