After the terrorist attacks in Manhattan on Sept. 11, 2001, there was speculation that the days of the skyscraper were over. But five years later there has been a resurgence in the skyscraper's popularity. This boom is fueled by a new approach to design -- designing for sustainability. E&ETV's Special Report, "Building the Tallest Green Buildings," takes you inside Manhattan's green skyscrapers and explains how they differ from conventional structures. Experts discuss how the green buildings trend has evolved and talk about the future of sustainable design. Click here to see the complete multimedia presentation.