Under the sea, under mountains, under cities. Railroads need these - somehow both well known and yet mysterious - works of faith, sweat and blood. Without tunnels the first railroads would have never left the immediate boundaries of their founding. No going west across the Appalachians. Conquering the Rockies would have meant a slow tortuous route of switchbacks. 10 million people a year would not be heading quickly and efficiently by train between France and the United Kingdom.

The modern world of commerce began when railroads could reach every part of the land. And that means huge construction projects. Bridges, tunnels, snow sheds and much more…but the tunnels are what really brought railroads, and their freight, to all parts of a country.

Pentrex looks at the need for tunnels (why not a 10% grade?) and at some early and famous projects. Then it's a video look at several projects:
* Take a cab ride through Alaska's shared Whittier Tunnel
* The Twin Peaks Tunnel in San Francisco with vintage film
* Chicago Freight Tunnels w/ 40 Feet Below (and the '92 flood)
* Tour a series of original B&O tunnels in West Virginia
* Construction of the “Chunnel”
* And more...!