One of the most amazing green roofs in the world is at the School of Art, Design and Media at Nanyang Technological University in Singapore. I like that this building invites you to walk onto its' roof as if it were a hill.
ACROS Building in Japan - The building features a step-up façade laced with more than plants. The roof is part of a huge 1 million square foot building that features office space, shops, theater and museum. An eco friendly green roof!