The California Academy of Sciences--which houses over 26 million specimens--is a trove of natural history, and the planetarium, four-story rainforest, and coral reef ecosystem are just some of the exhibits that will keep guests entertained for a full day. The building itself is a wonder; designed by Renzo Piano, it has a curving 2.5-acre "living roof" of native plants, and acres of open-air glass structures. Don't miss Claude the albino alligator, who is somewhat of a local hero. Tickets are $34.95 for adults, $24.95 for children. Open Mon-Sat 9:30 a.m. - 5 p.m. Sun 11 a.m - 5 p.m.