This 13th century Gothic brick castle is the largest in the world by surface area.

A quirky bookstore hidden beneath a sea of whitewashed Greek villas.

Legend says this sacred tree was a gift from goddess Athena.

An ancient knight and a symbol of the city's freedom.

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

Northern Ireland's Brobdingnagian stepping stones.

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

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

A museum marks and documents the site of the Titanic's launch.

Ireland's most remarkable collection of these curious cone-shaped houses is worth the buzz.

A statue honoring 44 continuous years of greeting passing ships.

This kitschy tavern is also home to rare early editions of "Treasure Island."

The final resting place of the great navigator, or maybe his brother.

Single runway interrupted by a busy road that cuts across its middle.

The floor of this spectacular Baroque sanctuary is covered in memento mori.

Burial grounds for more than 1,000 bodies deep under the modern town of Rabat.

These temples are among the oldest free-standing stone buildings in the world.

An abandoned set from the 1980 film "Popeye," claimed and repurposed as a theme park by creative locals.

The largest free-standing aquarium in the world resides in a hotel lobby in Berlin.

A fascinating insight into daily life in the Eastern Bloc.

A preserved Nazi labor camp now has a Holocaust museum on site and memorials to the thousands that died while imprisoned at the camp.

These wire animal sculptures commemorate the exotic inhabitants that once called the Tower of London home.

These remote Florida islands have a history of sea turtles and sunken treasures, and one of the world's largest coastal brick fortresses.

Florida's oldest bar was once a morgue, complete with a hanging tree and gravestones.