Five sultans and their families rest in eternal splendor, teeming with overlooked beauty and drama.

A marvel of Byzantine engineering under the streets of Istanbul.

This replica of the Greek structure is in the heart of Nashville.

This mosaic dedicated to John Lennon was tended for years by a Beatles super-fan.

A stratovolcano located in the south of Iceland, with a long history of charted activity and a rich mythology attached.

This fantastical waterfall is hidden in a cave located in a cracked cliff.

Three columns of volcanic rock shoot out of the ocean.

The summer tourists on these cliffs are thousands of seabirds.

Iceland's largest geothermal mud pool is a little bit haunted and a little bit dangerous.

Saint Joseph was said to heal the deaf and blind, but it was a much smaller miracle that got him canonized.

Cold war icon and onetime "hole" in the iron curtain.

A wunderkammer of exoticism immortalized by Tom Waits.

Once the tallest building in the world, this abandoned church is now a monument to the destruction of WWII.

Home to three historic ships from the age of Vikings.

A strangely forgotten claimant to the much contested title of "Source of the Nile."

A 15th-century granary that played the role of futuristic slave quarters in the world of 'Star Wars.'

This grand hydraulic installation has provided water for townspeople since the Middle Ages.

A seemingly simple canyon that was the backdrop to a number of famous movies.

Founded in 670, this ancient mosque is an architectural time portal.

The other side is actually green.

Thousands of narrow alleyways in an ancient medieval city make up what's believed to be the world's largest car-free urban zone.

The oldest known university in the world is in Fez, Morocco.

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.