A cable-stayed bridge has one or more towers (or pylons), from which cables support the bridge deck.
There are two major classes of cable-stayed bridges: harp and fan.
In the harp design, the cables are nearly parallel so that the height of their attachment to the tower is similar to the distance from the tower to their mounting on the deck.
In the fan design, the cables all connect to or pass over the top of the towers. The fan design is structurally superior with minimum moment applied to the towers but for practical reasons the modified fan is preferred especially where many cables are necessary. In the modified fan arrangement the cables terminate near to the top of the tower but are spaced from each other sufficiently to allow better termination, improved environmental protection, and good access to individual cables for maintenance.
The cable-stayed bridge is optimal for spans longer than cantilever bridges, and shorter than suspension bridges. This is the range where cantilever bridges would rapidly grow heavier if the span was lengthened, and suspension bridge cabling would not be more economical if the span was shortened.
Designed by the French structural engineer Michel Virlogeux and British architect Norman Foster, it is the tallest bridge in the world with one mast's summit at 343.0 metres (1,125 ft) above the base of the structure. It is the 12th highest bridge deck in the world, being 270 metres (890 ft) between the road deck and the ground below.
Millau Viaduct is part of the A75-A71 autoroute axis from Paris to Montpellier. Construction cost was approximately €400 million. It was formally dedicated on 14 December 2004, inaugurated on the 15th, and opened to traffic on the 16th. The bridge has been consistently ranked as one of the great engineering achievements of all time. The bridge received the 2006 International Association for Bridge and Structural Engineering Outstanding Structure Award.