The bears of Bern have been a city highlight for over 500 years.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The birthplace of Karl Marx is now a museum dedicated to the communist revolutionary's life and work.

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

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

America's Most Wanted's set resides in this tribute to the history of crime and punishment.

The 5.5-mile ring of steel posts around the Capitol Building is one of the largest (and most uniform) of its kind in the world.

The grand marble structure next to the White House is Andrew Carnegie's temple to Pan-American diplomacy.

Disks are rolled out onto the south lawn to absorb the impact of Marine One's wheels like giant coffee coasters.

The preamble to the U.S. Constitution written entirely from vanity license plates hangs in the Smithsonian museum.

Look closely and you’ll notice that the color changes a third of the way up the tower.

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

A 1,100-ton train fell through the floor in 1953. Workers got it patched up in just 72 hours.

A derelict bit of infrastructure from the canal that once ran through D.C. is landlocked in the heart of the city.

An overlooked memorial honoring the local Washington residents who died in World War I.

A hidden passageway now marks the site of an assassination attempt on Ronald Reagan that some say broke a 140-year-old curse.

A muscular Art Deco monument represents the struggle between regulators and unbridled markets.

This seemingly out-of-place gas station by the Watergate hotel was once described as the most expensive gas station in the world.

Need a hardcopy of the 50-title Code of Federal Regulations? This is the place.

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

Before Metro, Washington had a robust streetcar network—and you see the remains of this infrastructure if you know where to look.

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

The little-known, 300-year history of the area includes former lives as a bustling tobacco port, parking lot, and industrial dump.

A building shaped like the Army Corps of Engineers logo, because why not?