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 . It comprises a pair of separate bores that ran parallel to one another at a distance of from the centerline of one another. 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. The ground proved to be relatively consistent, particularly in terms of hardness, throughout the boring process, which typically advanced at a rate of 16 meters per day. The tunnel was lined with prefabricated cement voissoirs, ring-shaped supports, that was manufactured used some the excavated material onsite. On 5 May 2005, breakthrough in the eastern bore was achieved, with the occasion marked by an inauguration ceremony presided over the Minister of Public Works
Magdalena Alvarez. One month later, breakthrough occurred in the western bore as well. == References ==