The Millau Viaduct in southern France began with a summer traffic jam. In the 1980s the A75 and A71 autoroutes ran from Paris toward Spain, but at the town of Millau drivers had to leave the highway, descend into the Tarn River gorge, cross a single old bridge, and climb back out, leaving holiday traffic and freight trucks stuck for hours. Planners weighed a Great Eastern route, a Great Western route that would have hurt villages like Peyre, a route near the RN9, and an intermediate route across the widest part of the valley, which was chosen in 1989. A low option with a tunnel would have hit the water table, so in 1996 a jury picked a high bridge designed by French engineer Michel Virlogeux and English architect Norman Foster.

The cable-stayed bridge is 2,460 meters long with seven pylons, six central spans of 342 meters, and a 36,000 ton deck shaped like an upside-down airplane wing so crosswinds press it down. Pylon P2 reaches 343 meters, and it was the tallest bridge in the world for over two decades. The Eiffage group paid about 394 million euros in exchange for toll rights until 2080. Work began in October 2001 and the bridge opened ahead of schedule in December 2004. It was so beautiful that sightseers braked to take photos, and the speed limit was cut to 110 kilometers per hour.

• Climbing formwork that poured concrete every 20 minutes and raised pylons four meters every three days
• Launching the deck from both plateaus with hydraulic wedges that moved it 600 millimeters every four minutes
• Twelve fiber optic sensors at the base of P2 that detect movement down to a micrometer, 100 times per second
• Piezoelectric sensors in the road that weigh vehicles and sort them into 14 types, and a flexible bitumen that took two years to develop
• Opposition from the World Wildlife Fund and local businesses, and Arnold Schwarzenegger’s office asking Millau for data