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

The oldest continuously operating fish market in the United States.

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

D.C.'s first central library was born out of a chance encounter with the philanthropist whose name it bears.

A much-maligned monument to teetotalism.

The privately owned cemetery that holds room for Washington's finest when they step down from life.

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

A tiny piece of the Moon is embedded in this stained glass masterpiece.

The sci-fi villain is a little-known inhabitant of the U.S. capital's largest cathedral.

This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The medieval castle built as headquarters for the Pope's secretive Knights Templar.

A king's pet, a pope's gift, an artist's inspiration, and a tragic shipwreck.

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

The top of society once luxuriated in this world-class hotel, which continues to impress, even in ruin.

Pilgrimage site for star-crossed lovers.

Hear the quietest sound from across the dome.

A neighborhood church's unusual abstract stained glass was the final project of avant-garde artist Jean Cocteau.

A mysterious spot where the laws of gravity seem not to apply.

The large fjord lake is thought to be the home of "Ogopogo," a giant sea serpent.

These locks on North America’s oldest canal are named after a porcine rock formation.

A mysterious lake provides fresh water without any source, somehow restoring itself from atop its mountaintop perch.

City law dictates that this mountaintop cathedral containing the heart of a saint is to remain the tallest building in town.

Futuristic apartment blocks are the backdrop for Montreal surfers hangin' ten on the Habitat '67 standing wave.