A curious cave church carved into the face of a cliff.

Budapest's Communist-era statues, banished to the suburbs.

A trail of iron footwear stands as a monument to the thousands executed along this riverbank during WWII.

Possibly the world's largest hourglass only needs to be reset every New Year's Eve.

This Hungarian castle was built out of cardboard and wood until it proved so popular that it got upgraded to stone.

Cave shrine on Monte Pellegrino.

Once the home of a hermetic monk, this cave now houses a small church.

This Budapest bar allows drinkers to leave their mark on the walls, floor, and even ceiling.

From Austrians to Nazis to Soviets, this historic Budapest fortress has a history as complex as the city itself.

An abandoned saucer-shaped monument in the Bulgarian mountains.

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

This brutalist monument is inscribed with 9921 names of Yugoslav partisans who perished during WWII.

Croatia's towering concrete blossom grows from the site of a World War II concentration camp.

This stunning, out-of-the-way Croatian monument commemorates a community's uprising against occupying fascist forces.

These warring psychedelic crags commemorate an unsuccessful military operation.

This spaceship-like Serbian monument reaches for the stars in celebration of the fallen fighters of fascism.

Space-age monument to an early 20th-century uprising.

This ironic war memorial thumbs its nose at a campaign of inedible humanitarian aid food products.

This museum preserves the hand-dug tunnel that kept Sarajevo afloat during the Serbian siege.

This historic cemetery was inaccessible for several years due to dozens of land mines.

This abandoned Olympic skiing facility still bears the scars of the Siege of Sarajevo.

A Biblically-based Natural History Museum.

This abandoned Navy base was transformed into an off-grid alternative living community for thousands of people.

A hand-built folk art installation covered with messages of God's love.