An obscure public service from the U.S. government that redeems burnt, moldy, and soiled old greenbacks.

The actual model from the original "Star Trek" series is now on display at the National Air and Space Museum.

There’s a hidden military meme engraved on the World War II Memorial.

A monument in Washington D.C. marks the spot from which all other roads were supposed to stem.

A three-story tower of books about Abraham Lincoln is one of the more unusual monuments to the president.

The walls of the iconic dome are hollow and have a secret stairway.

A hidden gem on the lawn of the U.S. Capitol Building designed by landscape architect Frederick Law Olmsted.

A cavernous three-story, 43,800-square-foot basement that was forgotten about for 60 years.

Home to items never before seen by the public.

One of corporate America's best-kept secrets is also one of the most publicly displayed.

A provocative museum dedicated to the genre and the harsh realities that inspired its origins.

An ancient Scottish rock formation said to be the gravesite of a giant remains ensconced in legend and intrigue.

Islanders once used this dramatic, otherworldly landscape to hide their cattle from Viking raiders.

This dramatic landscape hidden on the Isle of Skye looks as though you've stepped into the magical realm.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

This 17th-century street hidden beneath Edinburgh was once a breeding ground for the black death.

360° views of the city plus five floors of optical illusions and hands-on science.

The ritual has been performed uninterrupted for nearly 700 years.

These engineering masterpieces are a dominant feature of the Belfast skyline.

This Manchester laundromat is hiding something.

Small and slightly hidden, the American Writers Museum is preserving the legacy of America's finest authors.

To truly appreciate Detroit's landmark skyscraper, you have to step inside.

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

This sprawling bookstore spans four floors and has more than a million books in stock.