The Exposition of 1889 was also notable for its collection of 48 buildings illustrating the history of human habitation (\u00E0 l'histoire de l'habitation humaine), a display organized by Charles Garnier, architect of the Paris Op\u00E9ra.\u000a\u000aOrganized as a centennial celebration of the French Revolution, this was perhaps more important as a showcase of engineering technology than any other international exhibition of the 19th century. It boasted not only the highest structure then ever built, Gustave Eiffel's 300-m tower, but also that with the widest clear span, the Galerie des Machines (destr. 1910), a collaborative effort by the architect Charles-Louis-Ferdinand Dutert and the engineer Victor Contamin (1840-1898). The Galerie was 420 m long and had an unprecedented clear span of 115 m, accomplished with a novel system of thrice-articulated arches without intermediate supports. Even in much more eclectic structures, such as the Palais des Beaux-Arts and the Palais des Arts Lib\u00E9raux by Jean-Camille Formig\u00E9, deliberately exposed metal structural components were much in evidence. The Exposition of 1889 was also notable for its collection of 48 buildings illustrating the history of human habitation, a display organized by Charles Garnier, architect of the Paris Op\u00E9ra. The Eiffel Tower is the only remaining structure from the Exposition. Photographs remain; photographers include Adolphe Giraudon and Napoleon Dufeu.