This is the story of “MPK 20”–Facebook’s new flagship building on its Menlo Park campus. The hacker warehouse, designed by renowned architect Frank Gehry, is a 430,000-square-foot LEED-certified building tucked into the terrain like a Bilbo Baggins hut, where it will house a little under a third of Facebook’s global team.

The design is one big room because it’s meant to reflect Facebook’s open culture. Teams can sit together in one spot rather than be divided by offices and cubicles. The building’s parking lot is hidden away underneath the structure, reducing the eyesore and the urban island heat effects. And a green roof is designed to act like a park on top of a building. It’s a massive 9 acres of grass, complete with 400 trees and a half-mile walking loop.

Gehry Partners, LLP

Last night, Facebook allowed some of Instagram’s elite photographers to enter the space for the first time. That’s why the photos you see here have a propensity for Hudson filters. Today, the new building opens for business, though we’re told it will take some time for employees to fully inhabit the space.

Bigger picture, Facebook has just fired the first shot in Silicon Valley’s latest war–the one about “who has the most architecturally impressive offices?” Apple is building a giant clickwheel designed by Norman Foster, while Google just shared plans for a modular canopy designed by Thomas Heatherwick and Bjarke Ingels Group. It’s worth noting that Facebook recently spent $400 million acquiring an additional 56 acres directly across the street from its new Gehry. What exactly that space is for, Facebook has yet to say.

Of course, none of these visions has yet solved the more practical problems facing the companies and the once-quaint Bay Area cities they’ve occupied. Traffic and housing shortages have become major issues across the region, and no green roof or expandable canopy–however enviable one may be–can solve that.