The World Trade Center and Sears Tower were record-setting skyscrapers made possible by cutting-edge engineering innovations, but just as these American icons set new standards in construction, dark and insidious forces were poised to undo it all.

Today's greatest skyscrapers use cutting-edge tech to build sky-high micro-cities within their walls, and these innovative mega-builds are becoming the new engineering icons in Chicago, Dubai, Beijing, and other twenty-first century metropolises.