Line 6 (Spanish: Línea 6 Circular) of the Madrid Metro opened originally between Cuatro Caminos and Pacifico in 1979.

[1][2] The line is made up of 28 stations with 115-metre platforms, linked by 23.472 km of wide gauge tunnel tracks.

Along its route are some of the large interchanges built in recent years: Moncloa, Príncipe Pío, Plaza Elíptica and Avenida de América, in addition to the correspondence with Cercanías Renfe in Nuevos Ministerios, Laguna and Méndez Álvaro (which also coincides with the South Bus Station of Madrid).

[3] On 2 August 2024, Metro Madrid announced that they plan to have platform screen doors installed at all stations on line 6.

This project is considered to be the first major step towards the eventual goal of fully driverless operations on the line.