One of the most easily accessible examples of the rare 1960s UFO houses.

A small Portuguese cottage formed between boulders in the countryside.

An early work of the architect Álvaro Siza Vieira, these swimming pools blend into the beach.

Building owners can take out tiles for free at this repository for historic building materials.

A wonderful museum dedicated to the local straw hat industry.

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

The walls of this medieval church are covered with perfectly preserved frescos, including a pristine example of the Dance of Death.

Inside this small chapel tucked away in the forest is one of the most well-preserved Danse Macabre frescos.

Tokyo’s only Vaudeville-cuckoo clock–steampunk-Victorian curio cabinet time piece.

This tiny museum hidden above a restaurant houses thousands of modern and traditional kites.

This ultra-modern wooden boardwalk turns the ocean into a swimming pool.

An ultra-modern diversity park in Denmark has turned an entire city block electric pink.

This bridge's unique architecture honors nautical heritage and encourages self-awareness.

This centuries-old hotel hides a network of secret cellars and passages once used by smugglers.

This Croatian computer club features such gaming relics as the infamous Virtual Boy and an 8-bit Pacman machine.

This military tunnel dates back to World War II and provides visitors with a little wartime adrenaline.

Now abandoned, the world's first torpedo factory is crumbling into the sea.

American soldiers discovered Europe's best one-liner at the end of World War II.

Trick water gardens from 1619 featuring a 200 piece mechanical theater powered by water.

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

Museum devoted to the artificial language of Esperanto.

A spherical "micro-nation" in the heart of Vienna.

A Swiss amusement park entirely dedicated to the theory of ancient astronauts.

This army of concretions is an unexplained geological phenomenon unlike anything else in the world.