A 17th-century doorway in a small Sabine village is a portal into the mysteries of alchemy.

Italy's third-largest Roman arena gives a peek into the underground operations beneath the ancient spectacles.

Contrary to what its name suggests, you won't find any bunnies here.

A 2,000-year-old engineering wonder hides beneath an Italian town.

Abbey built on the ruins of Roman catacombs.

This memorial commemorating fallen Swiss Guards of the French Revolution has been called the saddest stone in the world.

This historic covered bridge contains a series of macabre paintings that communicate one thing: everyone dies.

A vast Communist-era exhibition space in the Bulgarian capital.

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

An unfinished complex built for children from around the world sits abandoned on the Black Sea coastline.

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

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

Eastern Bloc nostalgia, anybody?

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

A spectacular Bulgarian cave resembling a devil's head with a waterfall rushing down its throat.

Bizarrely shaped rock formations in northwest Bulgaria come with equally bizarre legends.

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

"Unity, Creativity, Beauty."

A flamboyant five-story building in Bulgaria resembles a crawling snail.

A collection of art from Bulgaria's time as a communist state.

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.