"For historians of architecture, the main attraction is the Labrouste Reading Room on the second floor. When it opened in 1850, the design was revolutionary. The slender cast-iron columns that run down the center of the room, and the pierced leaf-patterned cast-iron arches that support the twin barrel vaults, allowed Labrouste to dispense with massive masonry and gives the room a buoyant airiness not usually associated with products of the industrial age. On a sunny day, with beams of light streaming over the heads of readers from the windows facing the Place du Panthéon, it can be one of the blissful interiors in Paris." Via NY Times: http://travel2.nytimes.com/2006/03/05/travel/05journeys.html Photo via @becoming_parisian on Instagram.