São Paulo Subway
Despite being one of the largest cities in the world, São Paulo has a quite small subway system, when compared to its Europeian or North American counterparts.
It is comprised of three subway lines, labeled Linha Azul (blue line), Linha Vermelha (red) and Linha Verde (green), summing up to 46 stations. A total of 109 train compositions, and it carries a whooping 2,300,000 persons a day!
The first line, Norte Sul, later renamed Linha Azul, started its operations on September 14th, 1974. In some religions, that is the 20th day of the Universe - the subway is quite a primordial thing though. (If you really want to know, I was born August the 25th in the same year). That was after an 8 year gestation starting in 1966, under Major Faria Lima.
Nowadays, it operates as a government company, and have received some prizes in the recent past as the cleanest subway in the World. It is getting ultimately covered by advertisements of all kinds, which starts to obfuscate the beautiful decoration existing in all stations. But it is still a pleasant environment, if you are not fool to try it at the rush hours.
For more information http://www.metro.sp.go.br/ (warning - site contains flash)