Don visits an old powerhouse in Buffalo. Later, he checks out a tunnel system from the early 1800s.

Don penetrates a former Nazi military compound, uncovers clandestine oil rigs in seemingly normal neighborhoods, and kayaks down the LA River revealing a rarely seen side of Los Angeles.

In Hawaii, the host explores a hi-tech tunnel bored into a volcano. He also uncovers secret bunkers and learns about ancient bloody rituals.

520 feet above Seattle, Don Wildman experiences the Emerald City from the outer rim of the Space Needle. Mosquito Fleet steamboats prove difficult to find in the icy waters surrounding the city.

Don goes to Oak Knoll Naval Hospital and an old WWII POW camp.

The host visits Arizona and checks out a secret missile silo and a lost gold mine.

Don goes rafting in Tennessee and checks out a secret moonshine operation. Also: a look at collapsing coal mines and prehistoric caves.

Don gets access to an isolated stronghold that once saved New York city, uncovers the fantasy island arsenal of the biggest arms dealer on earth, and scrambles around a forgotten relic once used to keep the depraved out of site.

Don explores Boston to uncover how this city has solved big problems with bold ideas -- from the first subway in the US to a waste treatment plant that helped clean up the infamous mess in it's harbor.

Don explores the hidden corners of New York City.

The host visits St. Louis and explores the city's willingness to embrace change through the years.

Don explores Pittsburgh's industrial wasteland and hi-tech wonders.

Don explores the Twin Cities of Minneapolis and Saint Paul, Minnesota, revealing the secret past of these sibling cities and their hidden underworlds.