Renzo Piano, the architect:
"A green roof, landscaped with native plant species, unifies the different functions. It undulates to accommodate the Academy's major components: the new planetarium, the Rainforest Exhibit and the Steinhart Aquarium entrance. In the center of this "Living Roof" a glazed skylight covers the Piazza, while other smaller skylights allow natural light into the exhibit space and provide natural ventilation."
New in 2008. If in San Francisco, not to be missed. Some great shots of the roof from a camera on a kite.