Visitors enjoying a Saturday afternoon at the man-made Piscinao de Ramos (big pool of Ramos) ride along the track that divides the an artificial pool from Guanabara Bay's beach (left) in Rio de Janeiro's North Zone. In 2001 the bay, where 70 percent of the city's sewage is dumped, was declared too polluted to swim in and the state of Rio de Janeiro created the piscinao to give North Zone residents clean water to enjoy. It holds 30 million litres of filtered and chlorinated seawater and can attract 80,00 visitors over a single, sweltering hot weekend. Despite its popularity, the piscinao (big pool) is controversial. Some north region residents believe it was built to keep them away from the luxurious south zone beaches. Nonetheless, thousands of people who live in the surrounding favelas visit throughout the summer.