This long, dark tunnel is open to hikers, but those without lights are known to get confused even on the straight path.

"Not too many people can say they've had a nuclear bomb dropped on them, not too many would want to." — Walter Gregg.

A view-altering observatory at the University of Texas.

Landmark Chicago building narrowly avoided destruction.

A spectacular remnant of an Adler and Sullivan masterpiece that was destroyed in 1972.

Partially submerged Buddha heads freckle Chicago’s neighborhoods.

One of the few remaining relics of the meatpacking hub that made Chicago the "hog butcher to the world."

An avant garde art museum at the University of Chicago.

One of the largest pieces of scientific equipment ever carried on a NASA space shuttle sits in a Chicago alley.

Chicago's North Park Village was once the largest municipal sanatorium in the country.

The world's only known button museum.

Years of archaeology, just chillin' by the water cooler.

These abandoned grain silos and tunnels are an urban exploration dream.

Nonprofit art center that promotes outsider, intuitive, and self-taught art.

A hollow cement depiction of time's inexorable effect on the human body.

This massive stained-glass masterpiece is thought to be the largest Tiffany dome in existence.

A giant milk bottle from the 1930s beckons drivers to this diner.

A tiny plaque hidden miles into the Washington wilderness is all that remains to honor a shipwreck that left 18 people dead.

A 36-ton remnant of the last Ice Age now resides amid picturesque vineyards.

The oldest operating steam locomotive in Canada runs along this heritage railway.

The building features one of the last remaining free-floating spiral grand staircases in the U.S.

In the midst of a residential town in Washington exists a property saturated with one man's artistic creations.

Walking by this fence is like strolling along a portal to various fictional worlds.

The second tallest railway trestle bridge in America.