This cheese shop also houses a museum devoted to Dutch dairy.

The attic of a four-century-old canal house hides a clandestine church.

This historic Amsterdam bar used to accept sailor's monkeys as payment.

Where royalty waits in the height of luxury.

Some 80,000 Delft Blue tiles line the inside of this Amsterdam walkway.

This 22-floor tower's Skydeck offers panoramic views of Amsterdam.

If you look closely at the oldest bridge in Paris, you might notice hundreds of ugly faces leering from its sides.

This bridge was constructed from the rubble of the infamous Bastille.

This city square is home to Amsterdam's oldest church and a statue honoring Dutch sex workers.

The location where the American Revolution ended.

The remains of Martha, the last known passenger pigeon, serve as a tool to educate about conservation.

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

While most wind tunnels test scale models, the "Cave of Winds" was large enough for actual airplanes.

A line of blue paint marks the route of the inaugural parade.

The bank that helped fund the Mexican-American War and the purchase of Alaska met its downfall after helping Augusto Pinochet launder money.

D.C. once had its own tiny rival to the New York Stock Exchange.

Beneath unsuspecting visitors feet, a capsule containing pieces of America’s civil rights history.

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

This nine-story building is the oldest standing skyscraper in D.C.

Once home to the largest photo service in the United States.

A replica of the famous memorial statue at the Normandy American Cemetery hides in an office building in downtown D.C.

This unassuming passageway played a key role in one of the most important events in U.S. history.

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

Light bulbs, scrap wood, and tinfoil comprise this homemade throne of the gods.