The world's third-largest crystal sphere has sat in the Penn Museum since 1927 with the exception of one outlandish theft.

A small museum along the Susquehanna River is home to a rich collection of Native American artifacts.

These termites have an large and deadly abode—impressive by day, dazzling by night.

Giant reed houses made in the marshes of Southern Iraq.

9th century Abbasid mosque, damaged in modern warfare.

Celebrated as a center of civilization, the remains of the ancient city have been nearly destroyed by greed, egoism, and war.

A geological oddity topped with a 2,000-year-old pagan temple.

Take respite inside this jaw-dropping church while climbing the volcano where Georgia's Prometheus was once chained.

An underground city of salt.

The walls and ceiling of this Polish church are decorated with thousands of skulls, with another 21,000 skeletons just below.

These Nubian pyramids are strange and unique, even by pyramid standards.

Egyptian treasure trove of fossils documenting the whale's transition from land mammal to sea creature.

An endless sea of white conical domes.

One of the most well-preserved temples of ancient Egypt.

A rare cluster of alien-like plants grows along a dusty highway.

A public display of prehistoric space rocks is named for the Namibian village where they were found.

Bizarre living fossil only grows in a small chunk of the Namib Desert.

Unexplained bald patches in the landscape grow and recede over time, as though they are somehow alive.

This "dead marsh" sits among the largest sand dunes in the world, a forest frozen in time.

A desert that rolls right up to the ocean, where it's so dry animals live off the fog.

The remains of diamond fever taken over by the desert.

This remarkably well-preserved mosque stands amid an 11th-century caravansary.

Five ancient libraries, little changed for centuries, preserve a medieval archive of Quranic lore and civic documents

These mysterious 1,000-year-old walls have revealed little about their past.