Eco-friendly office buildings aren't exactly unheard of, but we can't recall seeing anything matching the scale of this skyscraper Hao Ko and his associates at Gensler have designed for PNC Bank. Excavation work has already begun in Pittsburgh, the home of this "breathable" building that will feature a sophisticated double-skin ventilation system allowing fresh air to be pulled in and dispersed throughout its 33 floors — at least when local northeast weather permits it. A solar chimney will pull stale, warm air out of the tower. Preserving natural light was also a key design focus, with Ko and his colleagues laying out the building so that over 90 percent of floorspace would be covered by the sun's rays.

But the connection to the outside world will be made even stronger with SkyGardens; these collaboration-focused hubs will contain special areas that mimic outdoor weather conditions. That means employees will have to bundle up in the colder months and dress lightly in the dead of summer. Additionally, aside from serving as PNC Bank's new global headquarters, the space has also been developed with local residents in mind. A communal lobby will be open to all visitors, and plans even call for a 300-seat theater available for public use during non-business hours. You'll find more in-depth coverage of PNC Bank's skyscraper over at Fast Company.