Most great civilizations have some architectual history left behind that represents who they were as a people.  Egypt had the Great Pyramids, Greece had the Parthenon, Rome had the Coloseum along with many others.  We live in a time and culture where we build gargantum structures but tear them down fifty years later to build something more modern.  I'm curious what American buildings/monuments will still exist 2,000 years from now.