In a wooded area in Meudon, 10 km southwest of Paris, the landscape architect André Le Nôtrea designed a hangar where the French military developed balloons and airships. The filigree wrought iron structure was completed in 1879 using materials from the Grande Galerie des Machines designed by Henri de Dion – an exhibition hall for machine tools built at the Champ de Mars for the Paris World’s Fair in 1878 that was subsequently dismantled. Measuring 70 m long and 23 m high, the military facility eventually became obsolete, going on to serve as an aviation museum before standing empty for some 50 years.