The haunting ruins of a military fortress turned astronomical observatory sit on a Sarajevo mountaintop.

A war-torn Olympic relic is being overtaken by graffiti and nature.

This cluster of little wooden huts once ground local farmers’ wheat into flour during the days of the Austro-Hungarian Empire.

This ancient theater, restored in the 20th century, lives on as a venue for dramatic and musical performances.

This historic black and white monastery is one of Bulgaria's architectural jewels.

An architectural marvel that spans the Arda River, and has stories of a haunted past.

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

Nine centuries-old fortresses guard the walls of this medieval Romanian city.

This enormous abandoned prison was once dubbed the "Bastille of Romania."

A fire once nearly devoured this gorgeous 14th-century Gothic cathedral.

The European towns of Brașov and Râșnov each have proud signs reminiscent of the Hollywood sign.

This massive underground salt mine now holds a sci-fi theme park in its depths.

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

A tiny church on a man-made island in the Adriatic.

These historic defenses ensured the city within would survive hundreds of years of occupations, sieges, and invasions.

The ceiling of this cavern is dripping with multicolored marble stalactites.

Two distorted Romanesque columns hold aloft a mine cart in honor of laborers who died during WWII.

A 11-foot former president stands on a Kosovo street that also bears his name.

A futuristic, brutalist masterpiece that is also strangely prison-like.

Formerly Yugoslavia's "forbidden island," this sleepy little city still holds the abandoned remains of military strongholds.

The now-overgrown beach resort was once frequented by Yugoslav military elite.

This former estate of a fascist leader is now a burnt out ruin leading to a system of secret tunnels.

Once a state-of-the-art tuberculosis treatment spa, these ruins are now ruled by paintball players.

Gargoyle head that brings good luck.