A 19th-century subterranean reservoir repurposed as a contemporary art cave.

This sublime architectural marvel is a rare example of an expressionist church.

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

The once-abandoned 140-year-old hotel used in the movie "In Dreams."

The highest point in the state of New Hampshire, and while unlikely "the worst weather in the world," it sure seems that way to hikers.

One New Hampshire alleyway has become home to a public gallery of feline art.

Around 100 sculptures from artists all over the world decorate the hiking trails surrounding this locale.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

This narrow canyon has been carved by the river over thousands of years into spectacular and curious forms.

Even Henry David Thoreau found this glacial pothole irresistible.

Ruins of the elaborate house where the enigmatic costume designer threw glamorous parties for New York's theatrical elite.

The "World's Largest Underground Business Complex," a 55,000,000-square-foot city underneath Missouri.

Hundreds of graffiti artists have decorated this flood-wall on the west bank of the Mississippi River.

One of the world's earliest skyscrapers.

The Old Courthouse takes visitors on a captivating trip through St. Louis' timeline.

A big museum full of little worlds.

This is not your typical jungle gym.

A creepy sculpture of a decapitated head invites viewers to see St. Louis through its empty eyes.

Less a museum than a bizarre fantasy world created by artists and engineers.

This elegant arc of a waterfall marks a religious turning point.

The most powerful waterfall in all of Europe.

Climb right into the heart of this colorful Iceland volcano.

This modern monument to pagan belief looks like it was transported straight from ancient times.

An encyclopedic collection of mammal penises.