Mile-long cave system near Great Smoky Mountains.

The world's longest known cave system.

Internationally known record store and purveyor of "dusties."

Glass and concrete building designed by Albert Kahn.

A gothic church spire sits atop this skyscraper, the tallest church in the world.

Strange physical sensations and optical contradictions keep visitors coming back for more.

The fifth-longest suspension bridge the world, connecting one Michigan peninsula to another.

The world's first time capsule lies behind a welded steel door in Atlanta.

This massive store is home to an eccentric collection of vintage, retro, and peculiar goods.

This shop specializes in oddities and Victorian-inspired wonders.

One of few lasting examples of the brief octagon craze that developed into folly.

Faceless white figures loom over the city from the rooftop.

San Francisco's oldest surviving monument and meeting place for 1906 survivors.

Nestled in the heart of San Francisco’s bustling Financial District stands a unique homage to the Mayan and Beaux Arts.

A still functioning vaudeville carousel that has operated for over a century boasts a colorful menagerie and past.

An office built to look like a giant basket.

World's largest Christmas store.

A sealed test tube said to hold Thomas Edison's dying breath was given to the inventor's friend and mentee, Henry Ford.

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

The 80-foot tire that looms over Michigan's I-94 was once a Ferris wheel in the New York World Fair.

Weighing 30,000 pounds, this monument represents Detroit's first industrial era.

Abandoned concert venue legendary for its rock counterculture.

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

One man's attempt to create an artistic wonder on a run-down block in Detroit.