Floresta da Tijuca, considered the world's largest urban forest, is a natural boundary separating the western part of the city from the rest. Unbelievably dense, this tropical rainforest is in fact a man-made project from the 19th century focused on preserving the sources of drinking water in the region. The Corcovado Mountain with Christ the Redeemer statue is one of its many peaks, also home to hundreds of species of animals and plants and declared a national park in 1961.