The largest cave shaft in the world is home to thousands of birds and popular with BASE jumpers.

A mysterious monument meant to be a guide into "an Age of Reason" was destroyed after an apparent bombing.

The simple log cabin of a famed loner and naturalist stands preserved as a symbol of the ultimate DIY lifestyle.

This hulking behemoth is actually five interconnected towers built in the 1960s.

One of the world's steepest streets seems to have houses sliding down it.

One of the world's longest murals depicts the history of diversity in Los Angeles.

This futuristically sylvan church is a glass-enclosed marvel of modern architecture.

France's Lilliputian park displays over 100 of the country's monuments for visitor perusal.

A petroglyph map of the upper Snake River carved by prehistoric hunter-gatherers.

A museum, art project, and institution that demands we look at the world around us in a strange new way.

This huge concrete map of Scotland was built as a thank you gift from a Polish soldier.

A landscape of massive spherical boulders are the main attraction in this Kansas State Park.

The world's tallest doric column is this Ohio monument to a naval victory in the War of 1812.

This large midwestern cavern features impressive rock formations and an underground waterfall.

This lighthouse and shipwreck museum keep a torch burning for the memory of the SS Edmund Fitzgerald.

A collection of 1,300 accordions of all shapes and sizes displayed in chronological order.

Literally a million fascinating cartographic artifacts are held in this sprawling university collection.

These Great Lakes sea caves accessible by boat in the summer turn into temples of ice reachable by foot in the winter.

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

The only surviving prototype for Buckminster Fuller's house of the future.

This 1967 experiment in modular architecture was designed to be a new model for urban living.

Hell on Earth is actually a small town in Michigan where anyone can be mayor for a day.

The Beaux-Arts aquarium boasts a vast collection of saltwater and freshwater fish on an island in the Detroit River.

Controversial tribute to the heavyweight champion boxer who grew up in Detroit.