Founded in 1869, this classic museum contains a ve...

Founded in 1869, this classic museum contains a veritable wonderland of more than 30 million artifacts including lots of menacing dinosaur skeletons as well as the Rose Center for Earth & Space, which has a cutting-edge planetarium. From October through May, the museum is home to the Butterfly Conservatory, a glasshouse featuring 500-plus butterflies from all over the world that will flutter about and land on your outstretched arm.
Free its last hour (4:45-5:45pm), and admission price is 'suggested' at all other times (so free, if you have the chutzpah to suggest $0). Central Park West & 79th St, Upper West Side.