Tunnel of the Big Hill, Monterrey, NL, Mexico (Área Conurbada Monterrey)

Before the Big Hill Tunnel was built, there were very few roads crossing the Big Hill between cities of Monterrey and San Pedro Garza García in Nuevo León, México. Even with the addition of the Túnel de la Loma Larga (its Spanish name), a lot of cars still use the old options. El Túnel, as it is called by the locals, is actually two tunnels. Each tunnel has three normal traffic lanes with a fourth lane for emergencies.