Fresh air, rustling leaves, and thousands of wildlife species—welcome to the Amazon rainforest. Covering more than 2,100,000 square miles, this South America treasure extends its branches across nine nations—Brazil, Peru, Colombia, Bolivia, Ecuador, French Guiana, Guyana, Suriname, and Venezuela. Today, the Amazon is home to more than 30 million people, but it also carries secrets of lost civilizations. Archaeologists recently discovered a network of cities here dating back 2,500 years.