The Sao Paulo Metro is the first underground transit system in Brazil and it began operations in 1974. It works alongside a larger company called the Companhia Paulista de Trens Metropolitanos (CPTM) and together they cover about 300 km of track and transport approximately 3.7 million people daily.

Sao Paulo is one of the largest cities in the world, with a population of 19 million. Its metro system consists of four colour-coded lines: Line 1-Blue, Line 2-Green, Line 3-Red and Line 5-Lilac. Line 4-Yellow is currently under construction and is due to start operating in late 2009.

The metro system carries 3.2 million passengers a day.

Image: Dozens of people take the escalators down to the subway to a linking city for the northern area, during rush morning hours at southeast subway station, in Sao Paulo, Brazil. | Photograph: Mauricio Lima/AFP/Getty Images.