This colonial tavern played host to George Washington, Thomas Jefferson, and other famous early Americans.

The tomb was guarded by soldiers from both sides of the war, and some left their initials carved in the brick.

Italy's third-largest Roman arena gives a peek into the underground operations beneath the ancient spectacles.

A copy of the famous statue can be found in this Florence piazza, along with one of the most breathtaking views of the city below.

The graveyard holding the remains of George Washington's slaves was forgotten for nearly 200 years.

A slightly creepy gallery of plaster cast models in the same museum as Michelangelo's David.

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

The Cold War-era "underground Pentagon" is a sprawling subterranean hideaway for the Defense Department.

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

One of the largest artillery pieces in the world sits in a Washington D.C. parking lot.

The U.S. Navy’s preposterously detailed mini battleship took 77,000 hours to complete.

Two stone columns flank the grand Venice square, but there were supposed to be three.

Those with a sharp eye can find the hidden image of a German Shepherd on the memorial's Mural Wall.

A treasure trove of Renaissance-era funerary art in a Roman church built on top of Nero's grave.

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

A mammoth pair of Civil War artillery guns abandoned out in the forest.

The ancient abodes are a testament to human ingenuity amid harsh climates.

This massive swimming pool is the high tech home to the human-powered submarine races.

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

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

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

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

The sculptor was instructed to add “stallion attributes” to the general's bronze mare.

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