The curious underground history of keeping Paris clean.

This statue was given to France by the United States to commemorate the centennial of the French Revolution.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

The footprint of a frustrated devil in Munich's Cathedral.

These bronze pamphlets remember a remarkable group of Germans who fearlessly opposed the Nazis in the very center of their power.

Daily jousts and dancing barrel makers in Munich's mechanical clock.

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

The marble facade hides a little-known medical museum with early surgical instruments and rare copies of canonical texts.

An extensive collection of reliquaries containing the bones of saints housed in the largest Catholic church in Venice.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

This community on a small Venetian island has taken to painting their houses in bright neon hues.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

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

This statue of the "father of television" stands prominently in the United States Capitol.

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

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

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

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

The beloved statue at the National Academy of Sciences is oh so inviting to sit on.

The walls of the iconic dome are hollow and have a secret stairway.

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