Pont du Gard
A dizzying feat of ancient hydraulic engineering, the Nîmes aqueduct originates at a freshwater mountain spring in Uzès and travels a total of 31 miles through what’s now the Languedoc-Rousillon region of southern France. For the most part, you wouldn't know that a super-old (we're talking built in the middle part of the first century) subterranean water tunnel is even there until the conduit emerges from underground and is carried across the Gardon River along the undisputed grande dame of Roman aqueduct bridges, the triple-span Pont du Gard.
While water stopped flowing along this monumental limestone arc bridge at some point during the 6th century, the 160-foot-tall structure — later used as a medieval toll bridge — remains an ingrained part of the landscape and a bona fide tour bus magnet that, as a centuries-old tourist attraction, ranks up there along the Eiffel Tower as one of France's most visited architectural landmarks. (It's the most visited ancient monument in the county). While never exactly low-key, the 1985 listing of Pont du Gard as a World Heritage Site only lead to the naturally stunning — and ecological sensitive — area around the bridge to become even more chaotic and congested. Recent improvements, however, have successfully mitigated the vehicular traffic and fairground atmospherics long-plaguing this remarkably preserved relic.