The World Trade Center project is about more than big buildings. “The process of thinking about this unique site expanded into an exercise in imagining a new future for the skyscraper in an increasingly dense and urbanized world. In a number of proposals, the towers are interconnected rather than autonomous, so that they work horizontally as well as vertically. In effect, they create another ground plane to accommodate the kinds of public spaces historically limited to the street: parks, gardens and cultural facilities. The nine diverse schemes all conceive of urban life as a vertical proposition – cities in the sky.”