In Boulogne-Billancourt, a short Metro ride from central Paris, the Musée des Années 30 dedicates its entire 3,000-square-meter collection to a single decade: some 800 sculptures and 2,000 paintings alongside Art Deco furniture, ceramics, and interior-design pieces by Jacques-Émile Ruhlmann and Jules Leleu. Works by Tamara de Lempicka and Juan Gris hang among scale models of 1930s townhouses — an entire aesthetic moment preserved in one building.