Make your reservation to have coffee with some kitties.

A museum dedicated to the history and exploration of both popular music and science fiction.

A walk through the historic city center, under the streets of Seattle.

A temple to modernity, tucked away amid Barcelona's more well known museums.

A beautiful but toxic fountain of mercury.

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

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

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

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

An extensive collection of reliquaries containing the bones of saints housed in the largest Catholic church in Venice.

Stone memorial that's said to predict the death of the pope and the site of the Cadaver Synod.

The Pope’s secret escape route.

This bronze boar's snout has been rubbed to a golden sheen by visitors seeking good fortune.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

The mummified relic of St. Antoninus.

This private skyway is filled with art and was expanded explicitly so that Hitler could appreciate a river.

Secret refuge and museum of the Duke of Florence.

The bomb-ravaged remains of of a colossal Neptune.

The doodles of a genius line the walls of a secret room under the Medici Chapel, where they were hidden for nearly 500 years.

A dismembered holy head stares out from her beautiful reliquary at the St. Dominic Basilica.

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

Hidden beneath the famous St. Peter's Basilica is a veritable city of the dead that may hold the remains of St. Peter himself.

The only "Egyptian" pyramid in Europe and the legendary tomb of Remus.

2300-year-old Roman road connecting the empire.