A mesmerizing reservoir nestled at the heart of a pre-Islamic Yemeni village.

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

The solemn exterior conceals an opulent interior of this 17th century church.

A neo-Gothic church built to thank God for saving the Emperor of Austria from an assassination.

An exquisite Baroque church in Vienna's old town.

This former insane asylum now holds a pathological anatomy museum.

Macabre museum devoted to historical Viennese murders.

This eccentric folly house was designed by Romanian thinker Bogdan-Petriceicu Hasdeu, with a helping hand from his deceased daughter's spirit.

This bone-filled cave got its name after they found 140 bear skeletons inside.

Romania's "Red Ravine" is a little-known natural wonder that bears a resemblance to the Grand Canyon.

Conspiracy theories and occult legends surround this mysterious natural rock formation.

One of the oldest churches in Romania is believed to have been built on the site of a pagan temple.

No one knows who built this strange cave of worship or exactly why.

This solitary monastery may hold the remains of Vlad the Impaler (but probably not).

The legendary cliffside castle of three-time Voivode of Wallachia, Vlad the Impaler.

This fairy-tale castle would make Dracula (who is said to have been imprisoned there) jealous.

Moss and stone turn this waterfall into an otherworldly liquid veil.

An homage to the medieval rulers of Bulgaria.

The temple that withstood the Nazis.

Ruins of an early Roman Christian church dating back to the 4th to 5th centuries.

A gigantic statue of a Russian soldier watches over the ancient city of Plovdiv, a prominent reminder of the Soviet period in Bulgaria.

A mountain pass in Bulgaria's Balkan Mountains was the site of four historic battles.

This massive stone and steel monument remembers a century-old battle that cost thousands of lives and nearly destroyed the city.

The second-largest Jewish temple in Bulgaria was deserted after World War II, seized by the communist government and then abandoned again.