The Universal Exhibition in Paris in 1878 had a huge Great Gallery of Machines, designed by Henri de Dion. Renard brought the structure to Chalais-Meudon for use as a balloon store and workshop. It was named Hangar Y (all buildings at the site were allocated a letter) and the building nearest to it, which was used for the production of hydrogen, was named Building Z. Hangar Y has dimensions of: length , width , height .