Hidden beneath the streets of London is a secret subway that only carried mail.

This ornate Victorian marketplace was the setting for Diagon Alley and the Leaky Cauldron in the Harry Potter films.

One of the few remaining casualties of the London Blitz, this destroyed church has become an enchanting public garden.

Catacombs turned marketplace.

A historic London pub with prison cells in the cellar and a "spy room" on the second floor.

The world's longest known cave system.

Fragments of architectural wonders from around the globe are embedded in the newspaper building's walls.

This replica of the Greek structure is in the heart of Nashville.

A crumbling mountain resort that looks like it was abandoned in an instant.

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

An angular maze of concrete in Grand Rapids acts both as public art and as a staircase for fish traveling upstream.

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

A Beaux-Arts triumph set to become Ford's innovation campus

Island where motor vehicles are banned -- home to the only carless highway in the United States.

This national park on the shore of Lake Michigan features remarkable dunes that lie at the heart of a Chippewa legend.

These enduring murals depicting a distinctly Marxist tribute to capitalism could not even be defeated by McCarthyism.

What was once the largest NFL stadium.

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

World's largest Christmas store.

Standing guard on top of an old, vacant ice cream shop.

Former self-sufficient mental institution now a planned community.

The world’s largest Masonic temple was saved by the White Stripes.

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