of nature and its immediate consequences, we will study the Rio Carioca watershed for its iconic abiotic, biotic and social status. It is unfortunately not valued by the city or many of its residents, but it will at least illustrate problems the city is facing in its everyday life but not in its political decisions. (See also here .) The watershed of Rio Carioca has been occupied by humans since the dawn of colonial occupation because of its fresh water, firstly by local farms, later by industries, and then finally by planned residential neighborhoods. The Carioca River was a source of fresh water for most of the settler population. In 1750 the river was diverted to supply the downtown Rio's fountains and the arches of Lapa aqueduct, which conducted the water, remains today. The aqueduct is now a historical monument is used as a bridge and is the most iconic element of this neighborhood. However, only a very few remember what was its original purpose. A city between hills and lowlands The geology of the city mainly separates the territory in two main classes that are hills of granite or gneiss and lowlands constituted by silt, sands or landfills. During the 20 th century many hills were used for landfill and wetlands filled to create more territory near the ocean and the bay. This territory has been highly transformed by built infrastructure, and even its national park, Parque Nacional da Tijuca , was reclaimed, at the end of the 19