Architect Renzo Piano's 2008 landmark LEED-certified green building houses 40,000 animals in a four-story rainforest, split-level aquarium and planetarium, all under a 'living roof' of wildflowers. Inside, butterflies flit around in the glass Osher Rainforest Dome, penguins waddle in the African Hall, and Claude the albino alligator stalks the mezzanine swamp. Don't miss the new Giants of Land and Sea exhibit, where you can brave an earthquake simulation, virtually climb a redwood and get lost in a fog room.
After the penguins nod off to sleep, the wild rumpus starts at the kids-only Penguins+Pajamas Sleepovers ($119 including snack and breakfast; ages five to 17, plus adult chaperones; 6pm to 8am) and the over-21 NightLife Thursdays ($15; 6pm to 10pm), when rainforest-themed cocktails encourage strange mating rituals. Kids also dig the basement Steinhart Aquarium, where they can duck inside a glass bubble to enter an Eel Garden, find Dorys in the tropical fish tanks and pet starfish in the hands-on Discovery Tidepool.