The second-largest natural arch in the Chartreuse Mountains.

Natural cathedral designed by Italian artist Giuliano Mauri.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

A submerged archeological park still holds the wonders of a Roman Sodom.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

At the foot of a waterfall lies a peaceful swimming lagoon and evidence of over 60,000 years of human habitation.

The building hides in plain sight in Ribadavia's historic Jewish quarter.

Thanks to an acoustic anomaly, this unassuming stone bench has heard one hundred years of secrets.

This stop on the Camino de Santiago stands high above the underwater ruins of a medieval town.

A 12th century church completely covered in shells.

Remarkably intact Roman stone fortifications have encircled this Spanish city for centuries.

Seaside ruins of a settlement that date back to the first century B.C.

In Spain, the ruins of a Roman military camp sit along a flooded section of a river.

Lyon's "Wall of the Silk Weavers" is one of the largest murals in Europe.

The development of this cliffside waterpark is representative of Mexico's history of co-op tourism developments.

The remnants of an archaeological camp stand within Tikal National Park.

Giant kites are flown during this Day of the Dead celebration in Guatemala.

Only a handful of these gorgeous historic waterwheels remain but even those are in danger from local unrest.

Amid the rubble of Aleppo's Old Quarter, part of a historic market has been restored and re-opened.

Ruins of the Crusaders' headquarters.

The Syrian headquarters of alleged hashish-smoking assassins.

What is left of the pillar of Saint Simeon, the voluntary martyr who climbed the column to give his sermons, remaining perched there for thirty-seven years.

This Roman relic was discovered in Scotland by a mudlarking ferryman.

This extraordinary Viking artifact has traveled throughout the city.