São Paulo is the fifth largest city in the world, and the largest in Brazil.

Not only is it the capital of Brazil, but it is also the richest city.

With a population of 19 million (11 million in the city proper), its metro system is relatively small (61 km. of track) when compared to its European or North American counterparts.

The first line, Norte-Sul (North-South), later renamed the "blue line" or Line 1 – Blue, was opened in 1972.

The present system consists of four colour-coded lines: Blue, Green, Red and Lilac. The Yellow is currently under construction and is due to start operating in late 2009.

The São Paulo Metro carries some 2,800,000 passengers a day, but does not cover the entire urban area in the city. Another company, Companhia Paulista de Trens Metropolitanos (CPTM), works along the metro system and runs a light rail service. Metro and CPTM are integrated through various stations, and have received awards in the past as one of the cleanest systems in the world.