California Academy of Sciences
The California Academy of Sciences is an unfortunately stuffy name for an institution that is anything but staid. The country's largest natural-history museum includes an aquarium, a planetarium, an enormous rain-forest exhibit under a 27-meter-tall (90-foot-tall) dome, and a living roof that looks like a science-fiction fantasy. A visit here can feel like a trip to an amusement park, with a series of attractions to check out, but all of them are educational. The building itself is part of the appeal of the Academy. (Like the nearby de Young, the old home of the California Academy of Sciences was damaged in the 1989 Loma Prieta earthquake, and starchitect Renzo Piano designed its very environmentally friendly replacement.) It would be easy to spend an entire day or more seeing all of the Academy's exhibits, so be prepared to pick and choose among them.