When the last of its employees made the move to Facebook's new Menlo Park, Calif. headquarters, CEO Mark Zuckerberg encouraged the newcomers to decorate and modify the new digs as they saw fit. During what was dubbed the "Space Hackathon", a group of 100 workers took to the roof and painted a giant, 42-square-foot QR code on the roof of one of the company's buildings. 

Where does the QR lead? To Facebook's QR page, of course. 

[NBC Bay Area via Ubergizmo]