The Dos Valires Tunnel links the River Valira del Nord with the River Valira d’Orient. At its western end the Tunnel ends over the Valira del Nord, spanned by two bridges because the Tunnel itself is split in two. These bridges end up in a large-diameter roundabout, placed at a considerable height above ground. The roundabout is situated on a rough terrain, which is what forced us to build it elevated in its most part. . The solution chosen was a prestressed concrete structure divided into six stretches, mutually connected by half joints. This is a major civil work, one of the most important ones ever undertaken in Andorra, second only to the large, recently built tunnels.