This small museum tucked within a subway station holds pieces from Madrid's past.

A spectacular walk on the flank of a gorge.

This is not your typical jungle gym.

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

Man-made geyser that rises to the exact height of the Gateway Arch.

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

Fresh wooden posts have been added to ancient holes to recreate a primitive henge clock.

Once one of the world's great cities, Cahokia was a place of religious worship, trade and mass human sacrifice before being mysteriously abandoned.

An abandoned factory along the Mississippi coated by a giant mural.

This ambitious restaurant celebrates the culinary traditions of the Ozarks before 1870.

One of the world's earliest skyscrapers.

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

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

A sculpture of a giant man escaping from the depths of the Earth.

This otherworldly church spire reaches up toward the heavens.

A beloved, quirky little fountain featuring a large frog spitting water at a naked boy.

An open-air "garden" of mural art that changes weekly.

The oldest giants in Catalonia are now displayed in a 14th-century Gothic church.

A vista of the city and sea from atop the little-known viewing deck on an unassuming Columbus statue.

A former steam-powered mill from the 1800s is now an industrial park with a giant steel dragon slide.

Gaudí's famously flamboyant architectural style is on full display in this sprawling park and garden.

A beautiful but toxic fountain of mercury.

Two towns are linked by an engineering marvel masquerading as a boring suspension bridge.

Giant topiary dog once played a role in a terrorist bomb plot.