Best approached from the rear, the old Commerce Exchange looks like a giant spaceship. Now home to an organization of food producers, it's worth a stop inside to see the beautifully restored iron-and-glass dome, which Victor Hugo dismissively likened to a jockey's cap. Built in 1809, this was the first iron structure in France. Behind it, the 100-foot-tall Colonne Medicis is a remnant of a mansion constructed in 1572 for Catherine de Medici. The column, which miraculously escaped destruction through the ages, was used as a platform for stargazing by her powerful astrologer, Cosimo Ruggieri. Legend has it that on stormy nights, a silhouetted figure can be seen in the metal cage at the top. To learn more about the building of the dome, check out the short video of its construction in the Musée des Arts and Métiers.
2 rue de Viarmes, Paris, 75001, France