This unique structure allowed boats to bypass underwater mine barriers in the channel to enter the harbor.

The oldest arboretum on the Dalmatian coast doubles as the gardens of Kings Landing in "Game of Thrones."

Longest fortress system anywhere in Europe.

The remains of a sunken military ship wreck visible through clear water.

Large, airy hallways hide within an impenetrable fortress that beckons urban explorers.

Where the lovelorn find a home for their sentimental keepsakes.

A musical instrument played by the sea.

A chain of 16 wondrous lakes formed as a result of the gradual dissolution of soluble layers of bedrock.

An ethereal glowing blue ocean cave in Croatia.

Resting in the middle of an Austrian river, this sci-fi "island" lets people cross in neon style.

The largest ice cave in the world is thought to be the entrance to hell according to Austrian legend.

Swarovski's museum/theme park is a fake diamond fantasia overlooked by a giant.

The world's longest tunnel with an undersea section.

A network of sandy streets lined with verdant fukugi trees weaves throughout this tiny seaside town.

One of the world's largest tanks mimics the experience of watching rare whale sharks, giant rays, and deep sea creatures from the ocean floor.

These Japanese gardens are blankets of light for dark winter nights.

The 43-mile route crosses through six islands with gorgeous views of the Seto Inland Sea.

One of Japan's most famous sights, the bridge was originally built in 1673.

Nine Gardens in one—with tea service.

This historical theme park celebrates all things noodle.

Every autumn, this hillside is ablaze with red summer cypress.