This crumbling medieval basilica once attracted pilgrims by the thousands to collect a miraculous dust that formed above the saint's tomb.

A section of the long chain that blocked enemy ships from entering Constantinople.

Legend says if you stick your thumb in the hole and it gets wet your wish will be granted.

Carvings in Turkey's Marble Road may have directed ancient Romans to a hidden brothel.

The ancient latrines of the Greeks, in all their public glory.

Over the centuries, this island paradise has done it all, from providing monks with ecclesiastical respite to sheltering an exiled Leon Trotsky.

A charming beach town in Turkey captures all the colors of the rainbow.

A small etching on the white marble parapet was written in runic script by a Viking mercenary.

Roman ruins, natural methane fires and a lovely beach.

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

In this historic region, homes and churches are carved into ancient volcanic rock formations.

Climb a steep hill in 90 seconds on the second-oldest urban subway in the world.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

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.

A monument to the two U.S. officers killed by North Korean troops while trying to trim a poplar tree.

The site of many tense prisoner exchanges across the Military Demarcation Line between North and South Korea.

Numerical symbolism abound at East Asia's oldest observatory.

The world's first cruise ship-shaped hotel is perched atop a cliff.

The darkest building on Earth was built for the snow-white scenery of the 2018 Winter Olympics.

Secret North Korean passage discovered below the world's most dangerous border.

Dyed by iron oxide over centuries, these sandstone rocks rise thousands of feet into the sky.

One of the largest Buddhist stupas in North America is built of concrete designed to last 1,000 years.

A focal point of in Denver’s skyline for over a century, inspired by a Venetian basilica.