In all of the 29 years it was in operation, no prisoners ever escaped successfully... or so they claim.

The U.S. Navy's last diesel-electric submarine rests half-submerged in the middle of Portland.

Home of Howard Hughes' Spruce Goose.

The wooden airship was the largest flying boat ever built.

A beautiful 62-acre Catholic shrine and botanical garden.

The seamy, underground secrets of Portland's criminal past.

Aqueducts have dramatically changed this old lake, now home to tufa towers and its very own species of tiny brine shrimp.

Standing in a state of "arrested decay," this ghost town allows for a detailed peek into Gold Rush life in an unusually harsh climate.

Hidden inside a gift shop that doubles as a museum, this gargantuan yo-yo can only be operated by crane.

This ultra-modern California span is actually a titanic solar clock in disguise built by famed architect Santiago Calatrava.

Canyon walls shrouded in ferns.

Two mammoth statues inspired by equally tall tales lure tourists to this roadside attraction.

These cinderblock farmhouses were actually World War II radar stations in disguise.