Americans Underground: Secret City of WWI

An amazing discovery has been made beneath a farm field in Northern France: a vast underground city where World War I soldiers, on both sides of the conflict, took refuge a century ago. Even more remarkable, it is one of hundreds of buried havens set up close to a 45-mile stretch of the Western Front. Follow American explorer and photographer Jeff Gusky as he documents one of these long forgotten shelters, and witness his attempts to connect the names of the American soldiers etched into the limestone walls to their living descendants.—Smithsonian Channel