Collapsing castle on the Hudson river was once the storage site of military surplus business.

Terrifying derelict military hospital once housed a recuperating Hitler.

Megachurch turned Catholic church comprised of 10,000 glass panes.

Fortified medieval tower house with lovely roof garden.

The world's largest vertical wind tunnel.

Walk through living pictures and music in the Cathedral of Images.

Surprisingly Delicious Asian-Style Hot Dogs.

A wall of chewing gum moonlights as collective art.

Venice's island of the dead.

One of the largest caves in the world open to the public.

Museum dedicated to awful artwork.

Treehouse motel and treehouse-building school.

Robots, lasers, and whoopee cushions, oh my!

A volcanic old faithful, Stromboli has been erupting continuously for the last 2000 years.

A collection of 20th-century automata, penny arcade games, and musical contraptions.

The Grand Canyon of Texas.

The mysterious wonder of an underground waterfall is illuminated by multicolored lights.

The summer tourists on these cliffs are thousands of seabirds.

This valley of hot springs and boiling mud pots is home to the record-holding "Geysir," which originated the English word.

A winding, blood-red tunnel of hardened lava navigable by foot.

A psychedelic labyrinth on the San Francisco bay.

These towering spires and glowing walls are carefully crafted from hundreds of thousands of icicles.

If a glacial river suddenly diving into a sheer chasm via a dramatic, multi-stage waterfall isn't peak Iceland, it's certainly close.

These slanted cubic abodes are a creative if odd solution to a zoning pickle.