A nostalgic bibliographic gem.

National Mall monument to the inventor of the screw propeller.

From this scenic rockface, you can still see the paths Western pioneers followed.

The tallest dam in Montana and top 10 in the country.

A treasure trove of artifacts dating back to the late 19th century in Alabama.

A statue in Enterprise, Alabama hailing the fast food giant Ronald McDonald, stylized as a boll weevil.

This 36-foot-tall bronze Lady Liberty holds a real flaming torch.

This funicular railway rumbles along for a mile up the nearly vertical face of Chattanooga’s Lookout Mountain.

Stroll among more than 50 large-scale sculptures created by world-class artists.

A cocktail lounge decorated like an American dive bar, in honor of the legendary author Ernest Hemingway.

An underground tropical garden sits inside a Paris Métro Station.

A large portion of this navigable canal runs under Paris's famed boulevards.

A lush vertical garden blooming in the heart of Paris.

Once a sewer culvert, this road tunnel now offers cyclists and pedestrians a subterranean stroll under the C&O Canal.

The legacy of a wealthy executive and his wife, this little-known art museum features works by Picasso, Monet, Renoir, Cezanne, and more.

The Conduit Road Schoolhouse is one of the last one-room schoolhouses remaining in Washington, D.C.

A rare example of a rural school in Washington, D.C.

The school tested mustard gas for the U.S. Army during World War I.

The only Civil War battle in Washington D.C. took place near this highest natural point in the city.

Washington's top-secret Cold War-era doomsday communications tower is located in a small neighborhood park.

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

She stares out across six lanes of traffic, clutching a musket and infant with determination.

The only remaining vespasienne in Paris is a (stinky) relic of Resistance.

It could once load ships with tons of coal in an hour before its closing in 1952.