A must for all museum and learning lovers, the California Academy of Sciences is in Golden Gate Park (if you take the bus from Market St, close to the hostel, you'll get to drive all the way down and check out Haight) and it's well worth a visit. Among the exhibits there's a four storey rainforest, where you can explore the plants and wildlife all the way up from the ground to the canopy, and a huge aquarium with areas from all over the world (including an albino alligator!). There's also an exhibit dedicated to Africa (Africa has penguins - who knew??).