You can row a boat through this ancient underground reservoir.

Started as a kitchen garden, now the second largest botanical garden in the world.

The fairy tale castle of the "fairy-tale king."

This futuristic German spa allows visitors to float in a pool of salt water while zoning out to underwater techno.

A whimsical and twisted animatronic monster tour beneath the streets of Berlin.

An eerie, derelict amusement park in Berlin.

One man's vision and a labor of love of many.

A turn-of-the-century architectural marvel built on healing mineral springs and salt licks.

Symbolic attempt to overcome the issues of life.

Once adorning a New York skyscraper, these reclaimed ruins now haunt an Indiana park.

A medical facility that has been kept frozen in time.

A hidden network of subterranean passageways lies tangled beneath Indianapolis' bustling City Market.

The longest navigable underground river in the United States is home to countless blind and albino animals.

Inside this magical collection, you can buy recipes cooked up by church ladies, motorcycle clubs, and clowns.

A rancher expanding a natural spring for his cattle came up with bones – lots and lots of them.

A fascinating collection of art made from petrified wood and fossils by two octogenarian twin brothers.

The two-cell building in Nebraska was briefly owned by a teenage boy and then a Hollywood dummy.

This replica small town lets visitors take a stroll through the story of progress in the U.S. via thousands of Americana artifacts.

Roaming bison and a spectacular view at the highest point in Nebraska.

America's smallest town is run by its single citizen/mayor/librarian/bartender.

An experimental, automotive replica of Stonehenge.

In rural Iowa, an imported 19th-century windmill overlooks an unlikely enclave of Danish culture.

Piled high inside this warehouse and coffee shop are salvaged goods that span every corner of the globe.

The “American Gothic" artist's largest works hang in an Iowa State University library.