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

One of several skulls claiming to belong to the beheaded St. John the Baptist is on display at this Roman church.

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

The skull of the patron saint of lovers lies in the Basilica di Santa Maria in Cosmedin—maybe.

19th century pendulum and a clock restored by a rogue group of guerilla artists.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

This former Roman Catholic Church still contains the embalmed hearts and organs of 22 popes.

Installed in an act of one-upsmanship, the annual sundial in this church is also a symbolic victory for the Gregorian calendar.

The middle finger of modernity.

A sculpture serving as an homage to Pope John Paul II.

A mysterious chasm in the heart of the ancient Roman Forum, the Lacus Curtius was once believed to be a gateway to hell.

The yawning maw of this pagan visage is said to bite off the hands of liars.

A deadly ancient portal to the underworld.

Rebuilt remains of a temple to Roman god Mithras.

The underground sanctuary of a mysterious ancient cult.

The world's second largest salt mine, said to have been discovered by Alexander the Great's horse.

The mysterious "Candelabra of the Andes" could represent anything from a god's trident to a hallucinogenic plant.

In this case, 'zero' marks the spot where the iconic Old Spanish Trail ends.

Peru's (not so) mysterious carved stones.

An unexpected desert oasis in South America.

One of the largest ancient geoglyphs in the world is a tall desert god used for predicting the weather.

Sparkling, calcite-covered skeletons of children who may have been sacrificed to appease an angry god.

A massive underwater sinkhole made famous by Jacques Cousteau.

A devastated ruin in the south of Belize where British explorers claimed to unearth the Mitchell-Hedges Crystal Skull.