Musée Océanographique
Perched dramatically on a cliff, this museum is a splendid Edwardian structure, built under Prince Albert I to house specimens collected on amateur explorations, including Jacques Cousteau–led missions from 1957 to 1988. The main floor exhibits the skeletons and taxidermy of enormous sea creatures, early submarines and diving gear dating to the Middle Ages, and a few interactive science displays. The main draw is the famous aquarium, a vast complex of backlighted tanks containing more than 6,000 species of fish, crab, and eel in pools running 100–450,000 liters.