Overview:Nazca remains one of the most mysterious sites on Earth. The vast desert floor is covered with hundreds of ancient geoglyphs depicting animals, human-like figures and strange geometric designs. But, many of these glyphs are so large they can only be fully viewed from the sky. Perhaps even more intriguing are the strange flat-topped mountains that appear to have had their peaks sliced off, and a band of man-sized holes that stretch for almost two miles across the desert. Could these ancient geoglyphs and mysterious landscapes hold the key to proving Earth was visited by aliens in the distant past? Ancient Astronaut theorist Giorgio Tsoukalos, along with author David Childress, investigates the origins and meanings of the mysterious symbols and shapes found in the desert of Peru.