This gigantic science-and-industry museum began life as an immense slaughterhouse. During construction in the 1960s, it was touted as the most modern of its kind. It turned out to be the center of a corruption scandal and was quickly abandoned when the city’s abattoirs were transferred elsewhere. After years of head-scratching, the building was finally turned into this terrific museum, which includes a planetarium, a 3-D movie theater, and a multimedia library, not to mention a real live submarine. The heart of the museum is Explora, two huge floors of interactive exhibits and displays, as well as excellent temporary exhibits. On the ground floor, parents will be delighted to find the Cité des Enfants (separate admission: 12€ adults, 9€ under 25 for a 1 1/2-hr. session; see website for hours; reservations essential, particularly during French school vacations), which has separate programs for 2- to 7-year-olds and 5- to 12-year-olds. Kids get to explore their own sensations and the world around them in a series of hands-on activities and displays. If all this isn’t enough, outside you can clamber into the Argonaut (access included with your ticket, must be over 3), a real submarine that was one of the stars of the French navy in the 1950s, or dip inside the gigantic metal sphere, called the Geode (adults 12€, under 25 9€,, an IMAX-type movie theater showing large screen films.