A few years back, Julien De Smedt Architects (JDS) wowed TreeHugger with a proposal for housing by the sea in Rimini, Italy,"that brings green roofs down to the ground and makes the roofscape part of the terrain." Roofing technology has evolved so much (or architects have become willing to take more risks) that roofs are no longer something on top of a building that you never see, but have become part of the visible and useable building.
That roof does a lot more than just provide seating though.
The huge overhang is calculated to shade the building's recessed glazing in summer;
In winter, the lower sun penetrates deeply and is absorbed by the thermal mass of the floors.
Fresh air is brought in through a long underground duct to moderate its temperature, run through a heat pump and finally circulated in the space. Top that off with stormwater collection and photovoltaics and you have a very green building. The architect writes that the building is:
based around sustainability, blocking the cold north Beijing winter wind, promoting the cool southeast summer wind, creating shadow to the south and moveable sun shading / solar cells to the east and west. The building becomes a result of a series of pragmatic scientific operations making a piece of architecture which is ingrained in the site and promotes the notion of low tech sustainability.