This abandoned convent keeps the tomb of a legendary beheaded princess.

A 16th-century monastery boasts a lush array of plants native to Mexico’s most biodiverse region.

A mysterious pillar in an ancient burial chamber is said to predict how long you have to live.

The only quarter of the Old City not dedicated to a major world religion.

This 6th-century church has the largest and best-preserved collection of Byzantine mosaics outside Constantinople.

An abandoned Byzantine fortress and notorious prison.

People have been living in the cave houses on this Italian hillside since the Neolithic era.

This gem is often wrongly overshadowed by the larger, newer Metropolis church in Athens.

An ancient tunnel in Jerusalem built to redirect water in the event of a siege is one of history’s great architectural innovations.

If you can look past the nearby sewer pipes, this urban sinkhole grotto is a mini-paradise.

Gladiators battle and chariots race daily in the ruins of a once-great Roman city.

The oldest burial ground in the city, final resting place of city founders, Ohlone natives and murderers alike.

A sulfuric hellscape in southern Italy.

This "second" cemetery represents New Orleans' attempt to keep cholera at bay.

Water and windows define this defensive Italian well.

A massive volcanic plug is now a protected area that hosts a number of bird species.

This beautifully deceptive waterfall is something far different from what it appears to be.

Southern Italy's spinning top village.

An underground paleo-Christian burial site composed of the remains of several cemeteries and Basilicas.

The once forbidden "secret cabinet" of erotic art from excavations of Pompeii and Herculaneum.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

A dead saint, a deadly poison, and a mysterious holy ooze.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

The stoutest tree in the world.