We've all heard of green roofs, but a company named Green Living Technologies even makes green walls. Their proprietary system of panels, made from recyclable aluminum or stainless steel, can go completely vertical yet are designed to be deep enough to support grass and even vegetables, while still allowing airflow and waterflow between it and the building.

Their wall on Pittsburgh's PNC building--the largest green wall in North America--supports some 15,000 "ferns, sedums, brass buttons and other plants" over its 2,400-square-foot surface. And while Gary Saulson, PNC's Head of Corporate Real Estate says "We really view the green wall as public art," it's art with benefits: They estimate the office space behind the wall will be about 25% cooler in the summertime.

via forecast earth