For World Rainforest Day we take you below these clouds to the Amazon River Basin and the largest rainforest in the world. Numbers help the story of this extraordinary place: At more than 2.1 million square miles, the Amazon accounts for half of Earth’s remaining tropical rainforests. And a fifth of the world’s fresh water flows through this river basin. Perhaps a tenth of the planet’s known species call it home, many of which have yet to be identified—that’s trees, plants, fish, mammals, and a third of Earth’s bird species. Now take a deep breath. The ‘Lungs of the World’ produces 20 percent of Earth’s oxygen, while storing vast amounts of carbon dioxide, earning it an all-star ‘carbon sink’ status.