Approximately 48,500 sf (4.500 m?) of various plants covers the undulating roof on this tri-wing gym (Dreifachturnhalle) in Buttenwiesen, Germany utilizing a three layered greenroof system by Optigr?n international AG / Optigreen. The sinuous ribbon of 8-10 cm thick substrate on the living roof was designed to blend seamlessly into the natural grassland landscape, and skylights look like shark fins protruding from a swaying sea of vegetation (Uwe Harzmann, personal communications, 2008).