Including these two latest proposed towers, Chicago has 11 planned or under-construction buildings of at least 800 feet in height. That's 10,696 feet in combined height — or roughly the equivalent of stacking seven Willis Towers on top each other. So if these new plans for 400 N. Lake Shore are not to go the way of the Chicago Spire, Related will have to establish the project in a hypercompetitive luxury condo market and, unlike 2008, hope the national economy continues to cooperate.