This is in a temporary location until 2008 (normally it is in Golden Gate Park, but now it is at 875 Howard). They had a rotating exhibit on the history of chocolate that my whole family enjoyed. The small section devoted to children under 5 was a bit unimpressive. They had a wide array of sea life in the aquarium, and if you can’t make it to one of the other Bay Area aquariums, this is a nice option. My 4-year-old enjoyed the hands-on fossil and bone tables located throughout.

The Academy of Sciences is located in Golden Gate Park and includes an aquarium and natural-history section. You can reach it using the Metro N line.

The aquarium had all the usual tanks of fish, including an impressive fish roundabout--you can follow the fish swimming around by walking upstairs to a circular tank. It's actually pretty cool as the lights are dimmed and you can just chill out watching the fish swim round and round. The aquarium also has a reptiles section, with a nice collection of snakes and a couple of alligators.

The natural-history section has a large display on earthquakes--San Francisco having been through a few--and there's a little interactive show that lets you experience an earthquake for yourself. I really liked the section on skulls--all sorts of skulls, from animals to humans. One whole wall is mounted all with skulls; it's very impressive. There's also an art display of the imagery of skulls, showing how its meaning changes according to culture. For instance, in Mexican culture, a skull is not particularly scary--children play with them as part of the Day of the Dead celebrations. There's also a skull gift shop, just the place to buy a present for your Mum.

NB: If you're using the tourist maps to find your way around in Golden Gate Park, the park is actually a lot narrower and a lot longer than depicted.