Dr. Joe Schwarcz gets to the root of gutta percha

Machu Picchu | This 15th-century Inca citadel is perched on a 2,430-meter (7,970 ft) mountain ridge in Peru. The name in Quechua possibly means "old mountain." The Incas constructed the estate around 1450 but abandoned it a century later during the Spanish conquest. At its peak, around 750 people, primarily support staff, lived there permanently. Farming was primarily conducted on the site's hundreds of man-made terraces. Machu Picchu is divided into an urban sector and an agricultural sector, a