The watery entrance for condemned prisoners heading to the Tower of London is still visible along the Thames.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

Six ravens are kept captive (but well-fed) at the Tower of London to prevent the fall of the Crown.

Take shelter from Hawai'i's tropical heat under the massive canopy of largest Banyan tree on the island.

These ancient sacred grounds granted amnesty to those who managed to reach them.

A little marble compass above George Washington's (empty) tomb in the Capitol marks where D.C.'s four quadrants intersect.

Perhaps the most scandalous statue of America's first president.

All unmarked mute swans on the Thames are owned by the Queen per a tradition that began in the 12th century.

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.

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

It was once the base for a series of domestic terror attacks.

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

Washington's iconic carousel has a nice piece of Civil Rights history.

Members of Congress have traveled between the buildings on Capitol Hill for a century hidden from tourists, press, and storm clouds.

A heroic pigeon that, through a barrage of gunfire, delivered a message that saved over 100 lives in World War I.

The "lovely red Vega" of the legendary record-settling pilot.

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

A traveling postal dog covered 48 states and more than 140,000 miles, and he lives on as taxidermy, patched up with a rabbit's foot and a pig's ear.

The most decorated dog of World War I is preserved in the Smithsonian.

It's good luck to be mocked by this monkey.

Recently restored menagerie of Victorian-era beasts.

A harem-inspired Moorish fantasy design in a Victorian-era Welsh castle.

Famously misunderstood wonder of the ancient world

A six-ton wedding present for the King of the Scots.