The Viaduc de Garabit is a magnificant iron viaduct crossing the Truyère valley, near Ruynes-en-Margeride, Cantal, France, in the Massif Central region.
Constructed between 1882 and 1884. Opened in 1885. It is 565 m (1,854 ft) in length and has a principal arch with a span of 165 m (541 ft) and a rise of 52 m. Height at the crown: 10 m. Maximum height 122 m. Total length 564.7 m.
Designers: Gustave Eiffel, Maurice Koechlin, Léon Boyer.
Contractor: Compagnie des établissements Eiffel
Similar in design to Maria Pia Bridge, which had a similar arch span and lower height.
Numerous photos here.
See here[1] for information on design and construction.