Last fall, while le tout Paris and architecture enthusiasts worldwide were agog over the debut of Frank Gehry’s assertively spectacular and lavishly publicized Fondation Louis Vuitton in the Bois de Boulogne, a much finer building had just opened with no fanfare, some five miles to the southeast. Designed by Renzo Piano, the Fondation Jérôme Seydoux-Pathé in the 13th arrondissement (not far from Dominique Perrault’s glass-towered Bibliothèque Nationale François Mitterrand of 1989–1995) is a museum, archive, and cinematheque for Pathé, the pioneering French film company. With its ingenious demonstration of how to insert a work of avant-garde architecture into a historic setting, this voluptuously swelling aluminum-and-glass-clad form—instantly likened to an armadillo—ranks among Piano’s best works.