Rio de Janeiro, situated on Brazil's Atlantic coast, is one of the most densely populated cities in the world. The lush, forested hills surrounding the city and the dark blue waters of the bay below it lend Rio its unofficial name, the "Marvelous City." Despite its natural beauty, Rio is a city of contrasts. Run-down favelas, built from wooden planks and sheets of iron, stand alongside modern highrise buildings and elegant shopping malls. Great Cities of the World explores what makes Rio an exciting and vibrant world-class city.