The Bridge Portal
A bridge is a structure built to span physical obstacles without closing the way underneath such as a body of water, valley, or road, for the purpose of providing passage over the obstacle, usually something that can be detrimental to cross otherwise. There are many different designs that each serve a particular purpose and apply to different situations. Designs of bridges vary depending on the function of the bridge, the nature of the terrain where the bridge is constructed and anchored, the material used to make it, and the funds available to build it.
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The Pont du Gard is an ancient Roman aqueduct bridge that crosses the Gardon River in Vers-Pont-du-Gard near Remoulins, in the Gard département of southern France. It is part of the Nîmes aqueduct, a 50 km-long (31 mi) structure built by the Romans to carry water from a spring at Uzès to the Roman colony of Nemausus (Nîmes). Because the terrain between the two points is hilly, the aqueduct – built mostly underground – took a long, winding route that crossed the gorge of the Gardon, requiring the construction of an aqueduct bridge. Built in the 1st century AD, the Pont du Gard is the highest of all Roman aqueduct bridges and is the best preserved after the Aqueduct of Segovia. It was added to UNESCO's list of World Heritage Sites in 1985 because of its historical importance.
The bridge has three tiers of arches, standing 48.8 m (160 ft) high. The whole aqueduct descends in height by only 17 m (56 ft) over its entire length, while the bridge descends by a mere 2.5 cm (0.98 in) – a gradient of only 1 in 3,000 – which is indicative of the great precision that Roman engineers were able to achieve using only simple technology. The aqueduct formerly carried an estimated 200,000 m3 (44,000,000 imp gal) of water a day to the fountains, baths and homes of the citizens of Nîmes. It continued to be used possibly until the 6th century, with some parts used for significantly longer, but lack of maintenance after the 4th century meant that it became increasingly clogged by mineral deposits and debris that eventually choked off the flow of water.
Bridge types: Arch bridge, Aqueduct, Bailey bridge, Bascule bridge, Beam bridge, Box girder bridge, Cable-stayed bridge, Caisson, Cantilever bridge, Cantilever spar cable-stayed bridge, Clapper bridge, Covered bridge, Curling bridge, Drawbridge, Extradosed bridge, Folding bridge, Footbridge, Girder bridge, Inca rope bridge, Jetway, Lattice truss bridge, Log bridge, Mabey Logistic Support Bridge, Moon bridge, Plate girder bridge, Pontoon bridge, Retractable bridge, Self-anchored suspension bridge, Segmental bridge, Side-spar cable-stayed bridge, Simple suspension bridge, Skew arch bridge, Step-stone bridge, Stressed ribbon bridge, Submersible bridge, Suspension bridge, Swing bridge, Taper Suspension Bridge, Tied arch bridge, Tilt bridge, Through arch bridge, Toll bridge, Transporter bridge, Trestle, Truss arch bridge, Truss bridge, Tubular bridge, Vertical lift bridge, Viaduct, Vierendeel bridge, Vlotbrug, Weigh bridge, Zig-zag bridge
Individual bridges Akashi Kaikyo Bridge, Benjamin Franklin Bridge, Bronx-Whitestone Bridge, Brooklyn Bridge, Burlington Northern Railroad Bridge 5.1, Contoocook Railroad Bridge, Delaware Memorial Bridge, Forth Bridge, Golden Gate Bridge, Huey P. Long Bridge, Humber Bridge, Kintai Bridge, Lake Ponchartrain Causeway, Mackinac Bridge, Mike O'Callaghan - Pat Tillman Memorial Bridge, Millau Viaduct, New River Gorge Bridge, Pont de Normandie, Rion-Antirion Bridge, San Francisco - Oakland Bay Bridge (Eastern span replacement), San Mateo – Hayward Bridge, Stonecutters Bridge, Sunshine Skyway Bridge, Tacoma Narrows Bridge, Tappan Zee Bridge (replacement), Throgs Neck Bridge, Triborough Bridge, Tsing Ma Bridge, Verrazano-Narrows Bridge (please expand)