Guadarrama Tunnel

The Guadarrama Tunnel is part of the Spanish high speed rail network connecting Madrid and Valladolid and is one of the most important travel links in Spain. Crossing the Sierra de Guadarrama mountain peninsula, this double fornix tunnel is 16.5 miles long, with the widest of the two tunnels 33ft in diameter. The construction contract was signed in 2001, and work began soon after using a Tunnel Boring Machine, although progress was delayed by especially hard rock formations. The tunnel cost around $1.6 billion to build and upon completion, trains will be able to pass through at maximum speeds of 217mph.