This gigantic and terrific science and industry museum was built upon the site of the city’s former 19th-century slaughterhouse auction room, which had closed in 1974 due to competition from the suburban Rungis food market, leaving the city with derelict land to fill. Today it includes a planetarium, a 3D movie theater, and a multimedia library, not to mention a real live submarine. The heart of the museum is its permanent collection, which flaunts huge floors of interactive exhibits and displays on subjects like sound, mathematics, and human genes. On the ground floor, parents will be delighted to find the Cité des Enfants (separate admission, 12€ adults, 9€ under age 25 or over 65, for a 90-min. 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 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 age 3 to enter), 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 (12€ adults, 9€ age 25 and under;, an IMAX-type movie theater showing large-screen films.