An ancient Roman theatre restored to its former glory in the Spanish city of Cartegena.

The world's first electric battery-powered submarine.

This building has survived for more than a century and remains virtually untouched.

The mummified right fist of a 1,000-year-old saint-king sits inside an ornate golden reliquary.

The bust of Romania’s most notorious ruler, Vlad Dracula aka "Vlad the Impaler," keeps watch over the ruins of his medieval court.

This hauntingly beautiful cemetery outside a medieval citadel is full of winding paths and ivy-covered graves.

A medieval church built up to defend its village.

An interactive museum-like experience takes visitors back to 1980s Communist Bulgaria.

This building has two facades of clashing architectural designs.

A Bulgarian monument to Russia's role in World War II is constantly being painted in pop culture protest.

A striking symbol of the Bulgarian capital.

Sofia's legislative center is continuously reinventing itself.

"Holy Wisdom" overlooks the city that became its namesake.

An homage to the medieval rulers of Bulgaria.

A decaying, yet still functioning, work of communist architecture.

This sculpture used famed boxer Joe Louis as the inspiration behind its body.

Romania's triumphal arch looks out over Bucharest.

Historic beer hall in Bucharest with magnificent stained glass and a lively folk band.

The preserved arm of a third-century sorcerer is believed to have the power to lift curses and spells.

This memorial to the victims of the Romanian Revolution of 1989 is often compared to a potato on a skewer.

This once-derelict building is now one of the most beautiful bookstores in the world.

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

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

This snug medieval lane is one of the narrowest streets in the world.