An enchanting monastery in the Spanish countryside appears lifted from a fantasy tale.

A lush indoor jungle fills this bustling Madrid transportation hub.

Bacteria and algae give the salty water its bubblegum hue.

Mountain where Jesus was first tempted by the Devil.

Step inside the first house designed by Catalan architect Antoni Gaudí, considered to be one of the first Art Nouveau buildings.

This was the second largest mercury mine in the world and one of the oldest preserved mine complexes in Europe.

Castle and secret tunnel withstood a siege until its owner was killed by the Holy Roman Empire, while sitting on the toilet.

A hidden stream deep in the mountains creates one of the largest tufa waterfalls in Serbia.

For over 40 years, this quaint little house has teetered on a rock in the middle of a river.

This memorial park stands on the site of one of the largest mass executions of the Second World War.

This 14th century castle withstood years of battle but is now sliding off the hills into the Danube.

An abandoned 19th-century iron factory perched along the outskirts of an idyllic village.

This region of Slovakia boasts some of the most plentiful opal mines in the world.

The blood-soaked ruins of the castle where the murderous Blood Countess was walled in alive.

An unusual abandoned church damaged in World War II sits in a small village outside Moscow.

An abandoned town of skeletal wooden homes.

Abandoned castle was once a grand example of Russian privilege, built exclusively to win a frivolous bet between noblemen.

The world's second-largest excavated hole.

Moscow's other, lesser known kremlin is a fairytale-like cultural complex modeled after Old Russia.

This communist behemoth is the heaviest building in the world and a legacy of a brutal regime.

A giant portrait of an ancient king looms over the river.

The romantic botanic tunnel feels like a well-kept secret.

The possible imprisonment of Vlad the Impaler here earned the medieval castle its nickname, "Dracula's Castle."

A small town Romanian cemetery filled with darkly humorous gravestones.