The Guadarrama Tunnel was designed as the most substantial civil engineering work of the wider Madrid–Asturias high-speed rail line, facilitating the movement of trains between the capital and the major cities of the north and north-western portions of Spain at speeds of up to 350 km/h (220 mph).

[2] The route selected for the tunnel, which runs between the municipalities of Miraflores de la Sierra and Segovia, overlapped with the protected area of the Guadarrama massif.

At the time of its construction, during the first decade of the twenty first century, the Guadarrama Tunnel was described by Administrador de Infraestructuras Ferroviarias (ADIF) as being the largest civil engineering project in Spain.

The approach selected for the excavation phase was via four "double shield" tunnel boring machines (TBMs), the design of which was specially adapted to suit the local geology.

[4] As a means of minimise environmental impact, there was no use of intermediate stages during the construction process, which was a rare option for a high speed tunnel of such length.