Line C of the Buenos Aires Underground, that runs from Retiro to Constitución terminus, opened on 9 November 1934, and it has a length of 4.3 km (2.7 mi). It runs under Lima Sur, Bernardo de Irigoyen, Carlos Pellegrini, Esmeralda, la Plaza San Martín and Avenida Ramos Mejia streets. It not only connects to every other line on the system, but its termini at Retiro and Constitución also connect it to some of the most important commuter rail networks in Buenos Aires, such as the Mitre and Roca lines and also long-distance passenger services. It is thus an important artery in Buenos Aires' transport system. At the same time, it is also the shortest line in both terms of length and number of stations.

The Buenos Aires Underground, locally known as Subte, is a rapid transit system that serves the area of the city of Buenos Aires, Argentina. The first section of this network opened in 1913, making it the 13th earliest subway network in the world and the first underground railway in Latin America, the Southern Hemisphere, and the Spanish-speaking world, with the Madrid Metro opening five years later, in 1919. As of 2023, Buenos Aires is the only Argentine city with a metro system.