To the unwitting observer, that massive new hill in San Francisco’s Golden Gate Park might appear to be the work of geology. Closer inspection reveals skylights and solar panels on its surface, and a steady stream of trucks running by, carting in hundreds of animal and plant specimens—including a colony of live penguins and an 75-foot whale skeleton. The hill—part Bilbo Baggins, part Doctor Doolittle—is in fact the new $484 million California Academy of Sciences.

When the museum and research center opens in Septem-ber, it will include a four-story rain forest, a 212,000-gallon aquarium (enough to fill 100 cement trucks), and 410,000 square feet of lab and exhibition space. The rolling green roof is more than decorative: The sod insulates in the winter and wicks in cool air in the summer, and the roof’s plants keep millions of gallons of water from washing off into storm drains.

The roof helped win the building a platinum-level LEED certificate for its sustainable advances, but Renzo Piano, the museum’s architect, says the design goes beyond that: “We’re not LEED because we’re clever. We’ve made up a new alphabet of architecture.”