While not Turkey's deepest underground city, this subterranean redoubt is the largest.

Standing proud atop a Turkish bluff, this Ottoman palace has retained its grandeur despite being abandoned for centuries.

Foreign invaders almost left this lovely Caucasus palace alone—almost.

Fortified homes of highland warriors that are still in use today.

Underground monastery and fortress.

Rock-hewn monastery complex with hundreds of cave structures tucked away into the mountainside.

Luxury hotel turned into a refugee camp, then turned back into a luxury hotel.

This massive glowering Lenin head gazes out over eastern Siberia.

A uniquely authentic display of traditional Russian culture.

Intricate wood carvings on an island in Siberia.

3,000 market stands in five former Zeppelin hangars.

Flamboyant architecture from the turn of 20th century.

A black cat protests the City Guild in Riga's Old Town.

This tiny Bulgarian town offers a stunning location in the mountains and a storied history.

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

A striking symbol of the Bulgarian capital.

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

The western-most fortress on the Great Wall of China has gone from a strategic stronghold to a kitschy tourist carnival.

18m long sarcophagus of a constantly growing dead prophet.

The lovely lake that was naturally dammed, then naturally destroyed, then unnaturally saved.

One of the most ethnically diverse spots on the planet.

Lonely minaret stump of a destroyed city.

Extremely isolated Silk Road caravanserai in the middle of nowhere.

A sacred lake with thousands of sacred carp and a biblical history.