How were the great civilizations of the past able to build Stonehenge, the Pyramids, Egyptian obelisks, the Colosseum, and the Inca monuments -- without modern technology? That's the question that Nova and the BBC set out to answer. Recruiting engineers, architects, archaeologists, stonemasons, and other assorted craftsmen, they attempted to re-create these five wonders of ages past. With one stipulation: only resources available in the respective...