Mausoleum and Holy Seat of Antiochus I of Commagene.

The alleged house of the Virgin Mary is tucked away in a park and nature preserve on Mt. Koressos in Turkey and is holy to both Catholics and Muslims alike.

This mysterious cliffside carving of an ancient Hittite deity has baffled scholars for centuries.

This historic hotel preserves many treasures from its heyday hosting passengers on the Orient Express.

Quite possibly the oldest love poem known to humankind.

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

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

Flames have been burning within this mountain for more than 2,500 years.

Hidden just under the waters around this Turkish island are the ruins of a once great city.

This famous city eluded concrete detection until the early 2000's.

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

This hunter-gatherer architecture is believed to be the oldest religious complex known.

Roman ruins top white travertine terraces formed by ancient hot springs.

The oldest family-run luncheonette in New York, last renovated in 1948, still serves food and drinks the old-fashioned way.

This elegant arc of a waterfall marks a religious turning point.

An encyclopedic collection of mammal penises.

Iceland's largest lagoon is home to stunning multi-colored icebergs.

One of the tallest buildings in Iceland, and perhaps, the most visually impressive.

Medicinal spa created with the discharge from a geothermal energy plant.

These excavated burials from the Tarim Basin are wrapped in mystery.

The embalmed remains of the communist leader lie within a custom crystal coffin.

This Cold War–era underground city includes offices for Mao Zedong and Lin Biao.

Monks turned this mountain into a temple by digging grottoes, tunnels, and a huge pagoda-like hall.

Walled family complexes in Southern China.