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.

The line was constructed by the Compañía Hispano Argentina de Obras Públicas y Finanzas (CHADOPyF, Hispanic-Argentine Company for Public Works and Finances), headed by a Spanish nobleman, Rafael Benjumea, the Count of Guadalhorce.

[3] The line was subsequently opened in 1934 and extended from the present terminus at Constitución to Diagonal Norte in the centre of the city.

Siemens has modernised the signalling systems on the line, at a cost of $18 million which included the use of Communications-based train control (CBTC) in order to improve the line's frequency and potentially open up the possibility of automatic trains in the future.