The project involved the construction of a twin-bore railway tunnel with a length of 28.4 kilometers through the Central Spanish mountain range of the Sierra de Guadarrama to the north of Madrid, which was to form part of the new high-speed rail link between Madrid and Segovia. The route ran under the Manzanare National Park, where the predominant geology was granite, with a hardness of up to 160MPa.

The project developed into a race between four Double Shield TBMs, two of which were manufactured by Herrenknecht (S-201, S-202), and two by Wirth. One Herrenknecht machine and one Wirth machine at the north and south ends began tunnelling, culminating in a neck and neck finish. The competition contributed greatly to the success of the joint project: in just three years, nearly 58 kilometers of tunnel were bored, with a boring diameter of 9.51 meters - an impressive documentation of the machine principle's efficiency.