This vast World War II defense line was the site of a fierce battle.

An expansive complex of subterranean tunnels is all that remains of one of Europe's most formidable medieval fortresses.

The enormous 250-room Vanderbilt mansion conceals hidden doors and secret passageways.

The atmospheric road was never meant to be so creepy.

This Victorian-era public house has set the standard for pub-style elegance for over a hundred years.

It was once nicknamed "the most bombed hotel in Europe."

These barriers stand as stark reminders of Northern Ireland's troubled past.

The ruins of this medieval castle in Northern Ireland have inspired artists from C.S. Lewis to Led Zeppelin.

This tiny train shuttles passengers to one of Northern Ireland's most spectacular sights.

Northern Ireland's Brobdingnagian stepping stones.

This short bridge is the only thing connecting a tiny Irish island to the mainland.

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

Five candy-colored villages on the Italian Riviera.

The yawning maw of this pagan visage is said to bite off the hands of liars.

The gorgeous library at Trinity College is home to remarkable treasures of Irish identity.

On the Hudson resides one of the largest clocks in the world.

World Trade Center memorial likened to a woman's sexual organ.

The rusting remains are visible sticking out of the waters of the Delaware Bay.

World War II bunker still standing on the New Jersey beach.

Now abandoned, the first public health hospital in the U.S. saw more than one million immigrants from around the world.

Step inside Lucy, the world's largest "elephant."

The site of one of history's most indelible and horrific tragedies.

This former Imperial summer home was the venue for a royal slap that once echoed 'round the world.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.