Aqueduct at Nîmes in France

The Romans excelled at building complex delivery systems of tunnels, channels, bridges, and fountains to transport fresh water from far away. One of the best-preserved sections of a major aqueduct is the so-called Pont-du-Gard near Nîmes (ancient Nemausus) in France, erected in the late first century B.C.E. to serve the flourishing town there. Built of stones fitted together without clamps or mortar, the span soars 160 feet high and 875 feet long, carrying water along its topmost level from 35 miles away in a channel constructed to fall only one foot in height for every 3,000 feet in length so that the flow would remain steady but gentle. What sort of social and political organization would be necessary to construct such a system? (Hubertus Kanus / Science Source)