Bring your hiking shoes, wool socks, and thermal underwear for a stay in these cozy forest huts.

A series of modernist treehouse hotel rooms grace the outskirts of an Arctic forest.

Teeny tiny hotel on the coast of the Canary Islands.

This "flat geyser" bubbles up out of the ground periodically like a disappearing river.

Vibrant street art created with mixed media.

An archeological treasure trove stumbled upon by a couple of children.

A completely underwater art museum sends a stark message about humans' impact on the environment.

Stuck in the middle of a modern Madrid city block are the remains of a 19th century sports complex.

Religious dwelling in a Spanish volcano.

This quaint Spanish village agreed to be painted blue as a marketing stunt but found that they preferred it that way.

The earliest known map to show America, discovered by accident at a Paris bookshop.

This abandoned mansion has a window for every day of the year, and is a temple for ghost hunters.

An abandoned Indian-inspired mansion.

A Franco-era dam flooded (almost) everyone out of this centuries-old Aragonese town.

A living art gallery painted on a canvas of Monterey pine trees.

Now a pile of ruins and rubble, this was a lovely mountain town as recently as 1960.

This ancient Spanish castle sits high upon a hilltop.

On La Gomera, "Silbadors" communicate in a 4,000-word language of whistles.

A medieval village holds a very modern hotel.

Abandoned waterpark turned counter-culture mecca.

Famed architect Antoni Gaudi built this generous thank you gift to a friendly host who housed him during a job.

A Spanish forest is filled with mysterious stone carvings.

These secluded and abandoned anti-aircraft defenses have become one the most scenic viewpoints in Barcelona.

Madrid's romantically ornate crystal palace has been offering shelter to plants and art for over a century.