Tren subterráneo (underground train), or Subte as it is called for short by the Porteños, is the metro system in Buenos Aires. It is quick and frequent and not too complicated to understand. At rush hour however, it is likely that you will miss a couple of trains simply because there are too many people in it. There are 6 lines with letter labels (i.e. ‘A’, ‘B’ etc) and information about the train times can be obtained by calling a toll free number: 0800-555-1616 or at the website: http://transmetro.mobi/bai/ which is conveniently in English.
The Subte stations are worth a visit even if you’re not using the transport as they have some nice historic paintings, artworks and architecture. The whole subway system is controlled by one company: Metrovias S. A.