A Concrete Ribbon Through the Clouds

By Joseph Giovanni

Nothing prepares first-time travelers barreling up toward Paris on Autoroute 75 for the Millau Viaduct, a long and towering white apparition that suddenly appears around a bend of the Massif Central. Framed by the windshield, seven lithe, stately masts, each with fanning cables, sail 1½ miles across the Tarn Gorge, holding up a roadbed 885 feet above the Tarn River, above even the cloud line that often shrouds the valley.

 

From its ribbon cutting in 2004, the viaduct was destined for Guinness: When finished, it had the highest road deck in Europe, the tallest piers and highest bridge tower in the world, and the longest launch of a bridge deck. It even displaced the Eiffel Tower as the country's tallest structure. Engineers took the curvature of the Earth into their calculations. But more than a wonder of epic size and technology, the gracefully curved bridge, supported on needlelike piers, is a masterpiece of daring and majesty. It was clear from the start that this bridge is much more than an expedient path between points A and B.

Millau was infamous as one of France's worst traffic bottlenecks, clogged during the summer holiday migration between Paris and the Mediterranean. In 1993, the French department of public works staged an open competition to build a high bypass bridge between plateaus at the top of the gorge, based on an initial concept by its engineer, Michel Virlogeux, who proposed a multispan, cable-stayed bridge with a phalanx of seven masts supporting cable fans.

An observation commonly made about engineering is that a structure will be beautiful if it hews closely to the laws of physics, that "elegance" accrues naturally to designs that obey and embody the forces. After the inauguration, Mr. Virlogeux said in an engineering magazine: "The greatest art comes from making things very simple, but very elegant and perfectly adapted."

In fact there are many ways to embody forces in a design, and architect and engineer proceeded component by component to achieve elegance. In an unusual professional arrangement, Mr. Virlogeux joined the team that won the competition, Foster + Partners Architects. "We were driven by the scale of the idea and a shared passion for the poetic dimension of engineering and its sculptural potential," says Norman Foster in "Millau Viaduct," a slim monograph on the bridge.

The fusion of their efforts meant that Foster did not simply apply architectural motifs to a pre-engineered fact, but worked with the engineer in a feedback loop, each informing the other. Mr. Foster and his associates, including Alistair Lenczner, who led the Foster team from 2001, were involved both with the engineering and the design of the engineering. They designed the parts making up the whole, always guided by a desire to reduce them to their structural and visual essentials.

Mr. Foster set some concrete goals, inking "light & lightness" at the top of sketches published in "Millau Viaduct." He also wrote, "I wanted the structure to look as delicate as possible, almost floating. I wanted motorists to feel as if they were flying their cars."

The designers buried the foundations deeply, so that the piers supporting the bridge would shoot up from the ground like "blades of grass," Mr. Foster said, with no apparent support. From the base, the vector of the bridge is up, aspiring to height like the mighty trunk of a sequoia. The architects turned the pier into a hexagon with faceted sides that catch the light and reduce the apparent visual mass. They tapered the form as it rose, to express lighter structural loads and to minimize the profile. Already thin and minimal, the pier was then slit in its upper reaches to create a vertical groove that allowed the two resulting sides to flex and absorb horizontal deflections from movement of the roadway.

The architects extended the split at the top of the concrete pier beyond the roadway into the steel masts above, forming an A frame. From the valley below, each pier and mast merge to look like a single needle with an elongated eye: Foster's drawings, in fact, depict a thread piercing the eye of a needle.

Because a structural spine runs under the middle of the roadbed, the designers could attach the cable fans to the spine in a single row, rather than securing a double set of cables to beams at either edge of the road. That allowed the architects to taper the edges to a thin line, reducing the overall mass, increasing the sense of lightness. Extending the curve of Route 75 through the hills, they gently bent the bridge on a 12-mile radius, creating a smooth, shallow curve that gives motorists at either end a view of all the masts at the same time. The masts add up to a regatta.

The architects painted the cables white, so that they would disappear into the sky on overcast days, and complement the blue of clear skies. They banished any clutter, including signage. They illuminated the piers and the masts so that they appear to be bright exclamation points lofted in the night sky.

Over the past generation, some have questioned the tenets and viability of architectural modernism. The Millau Viaduct is an unapologetic and very successful proof of its value system—a Brancusi among bridges, reduced and streamlined to an essence. In the context of the Massif Central and the Tarn Gorge, it is a colossal piece of land art that completes the landscape, arguably making it better, adding majesty to the serenity of the hillscape. The viaduct occupies the air and lingers in the sky, only lightly tethered to the ground.

Tellingly, motorists who cross the bridge from the south often turn off just beyond the abutment at the north and turn around to park and admire the bridge they have just crossed. They came across a thrill, as though driving in the sky, and now they want to see it. The Viaduct Millau is a beautiful object as well as a beautiful experience.

—Mr. Giovannini is an architecture critic and designer based in New York and Los Angeles.

A version of this article appeared May 11, 2013, on page C15 in the U.S. edition of The Wall Street Journal, with the headline: A Concrete Ribbon Through the Clouds.