The tunnel under the Capitol Building where Congress takes out its trash.

Home to items never before seen by the public.

Part of a WWII submarine is lurking outside the Washington Navy Yard parking lot.

This lifelike sculpture of a policeman serves as a helpful reminder to watch out for crossing pedestrians.

A former major munitions plant that has been converted into a sprawling art space.

The narrowest house in America is seven feet of pure spite.

This advertisement for talcum powder was painted on the rock face and has since defied removal.

The last holdout of a pre-Civil War rebel who took the matter of slavery into his own hands.

Built by the patriotic residents of Boonsboro in a single day.

Experience the pivotal Civil War battle at this interactive museum.

A sharp bend in a dramatic river canyon cut through red rocks.

Legend has it that President Grant’s frequent drinking in the lobby gave rise to the term “lobbyist.”

The first memorial dedicated solely to the Black troops who fought for the Union.

A gorgeous mural outside a beloved D.C. restaurant pays homage to famous Black Americans.

The last bastion of Roman presence north of the Alps looms over a German town.

Underground attraction offering tours of the foundational ruins of a church nave that collapsed in 1674.

This still-celebrated home was a radical architectural experiment in 3D De Stijl.

The world's first fish doorbell monitors this water passageway.

The cutest way to stay safe in traffic.

This enormous storm barrier is one of the largest moving structures on Earth, with each arm taller than the Washington Monument.

Peek through a transparent pyramid and drink in the mountain made of books.

The bridges portrayed on EU currency aren't fictional anymore.

This unique sculpture proved invaluable when it saved a train from careening off the tracks.

A miniature city, once ruled by the Queen of the Netherlands.