This early version of the guillotine was used to execute the man responsible for its construction.

One of the world's tallest statues is also one of its most hated.

The only quarter of the Old City not dedicated to a major world religion.

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

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.

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

The maze-like transportation hub contains abandoned areas, derelict stores, and a resident bat colony.

The national park was once a plantation estate.

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

This small-town Connecticut restaurant gives each diner a free book from its vast library.

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

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

Architecture lovers won’t stop touching the National Gallery's 19.5 degree marble prow.

Locals dubbed it the "Owl Building" because of its bird-like appearance.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

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

Perhaps the tiniest sculpture in Saint Petersburg is a little bronze finch inspired by a song.

This gorgeous reading room houses the oldest and largest art history library in the Netherlands.

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

This innovative steam machine was no doubt the most famous of the pioneer locomotives.

An unexpected Easter egg lurks in the background of a cherub wall relief at the Breakers mansion.

The gorgeous entrances into the city's underbelly look more like grand halls than subway stops.

You could be standing at the site of one of D.C.'s most fatal tragedies and not even know it.

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