Fresh air, lush foliage, rustling leaves and calls of thousands of species of animals and birds—welcome to the Amazon rainforest. Covering nearly 7 million square kilometres, this ecological treasure in South America extends its branches across nine nations—Brazil, Peru, Colombia, Bolivia, Ecuador, French Guiana, Guyana, Suriname and Venezuela. Today, the Amazon has over 30 million human inhabitants, but it also carries secrets of lost civilisations, hinting at the existence of prehistoric humans. Earlier this year, archaeologists discovered an extensive network of cities here dating back 2,500 years.