Maria de Molina tunnel which will join paseo de la Castellana and Vel&#225;zquez street with the N-II highway (Madrid - Barcelona) will be the largest municipal underground work in Spain. The tunnel is 1171 meters long and it will absorbe a traffic of 30000 vehicles going out every day. The initial part of the tunnel has been designed as false tunnels made with foundation walls and slabs. The concrete has been cast over the ground and the tunnel has been excavated afterwards in order to minimize the effect of the work on Madrid traffic. Once a sufficient depth has been reached, two different construction systems have been proposed, depending on the conditions the tunnel finds in each case. The project presents some singular points in which the solutions adopted are structurally extraordinary.<br><br>El t&#250;nel viario de Mar&#237;a de Molina, que unir&#225; el Paseo de la Castellana y la calle Vel&#225;zquez con la N-II de Madrid a Barcelona, constituir&#225; la mayor obra municipal de pasos subterr&#225;neos. El t&#250;nel de un total de 1.171 m de longitud va a absorber una salida de tr&#225;fico de 30.000 veh&#237;culos diarios. En los tramos iniciales se han proyectado falsos t&#250;neles con pantallas y losas hormigonadas sobre el terreno y excavadas a posteriori, para minimizar los efectos tr&#225;fico. Cuando se alcanza una profundidad adecuada se ha planteado la ejecuci&#243;n de un t&#250;nel con dos sistemas constructivos diferentes, dependiendo de los condicionantes que se encuentran en cada momento. El proyecto presenta una serie de puntos singulares en los que las soluciones adoptadas son estructuralmente extraordinarias