ABSTRACT
RIO DE JANEIRO was built on the left margin of Guanabara Bay, between its quiet waters and the first elevations of the Orgaos mountains. From the very beginning, the hill and the beach were basic elements, not only in its geographical constitution but also in its social structure. The geological cleavages which originated the vast bay cut through the mountain range and depressed the soil, which was then isolated from the ocean. Later, the ground crumbled and this big hole was enlarged. An old river which had been stopped by sand mounds changed the edge of the coast into a swamp. This swamp is another geographical constant in the city's history. In fact, a good part of the history of Rio is devoted to efforts to dry out the ground on which it stands.
