According to legend, King Arthur killed a beast that dwelled beneath the waters of this Welsh lake.

A medieval abbey featured on 'Game of Thrones' that dates back to the 12th century.

It is said a heartbroken man visited the gap every day to stare blankly out at the sea.

A Victorian marvel of engineering is now a 21st-century tourist attraction.

This Italian-style temple replica has been threatening to fall off the Irish coast for hundreds of years.

Northern Ireland's Brobdingnagian stepping stones.

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

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

Perfectly preserved ancient monastery in an impossibly dramatic location on a rocky island in the Atlantic.

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

Old-fashioned knowledge and modern engineering create the world's only rotating boatlift.

The heads of two giant mythological water horses honor Scotland's horselord past.

A church that bred legends, and served as an inspiration for the Da Vinci Code.

Ruined 11th century abbey built by King David I in Edinburgh, Scotland.

Cemetery honors Americans who died during WWII and is the resting place of Gen. George S. Patton.

This magenta statue commemorates the legendary marriage between a mermaid and the city's founder.

This noble mash-up in eastern Luxembourg is part Medieval, part Renaissance, all castle.

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

A shoreline exhibit describing the disastrous first attempt by the French to colonize North America.

The 32nd president's sprawling cottage sits on an island enclave jointly managed by the U.S. and Canada.

A quarter mile off the coastal tip of Maine you'll find the "Beloved Island" of Franklin Delano Roosevelt.

A rare opportunity to drive across the ocean floor.

Iconic rock formations that allow for exploration during high or low tide.

These powerful, if squat, Canadian waterfalls flow in different directions depending on the time of day.