Laerdal Tunnel, Norway - Epic Engineering

About 5000 different blasts were conducted during the construction phase of Laerdal Tunnel, which stretches under Norway's mountainous and fjord-filled terrain for 15 miles, making it the longest completed road tunnel in the world. 

Driving through a windowless tunnel for 20 minutes can get a bit monotonous, so a team of psychologists and engineers focused on retaining driver concentration. Some solutions used in the Laerdal tunnel include bright blue lights and subtle curves that keep drivers engaged. Most important, though, is the fact that the tunnel is divided into several different sections, breaking up the drive and creating the impression that commuters are traveling through a handful of smaller tunnels.