A large grotto built in the 16th century amidst Florence's famous Boboli gardens.

Secret refuge and museum of the Duke of Florence.

Lavish royal estate punctuated with heated greenhouses.

This unique Renaissance castle was turned into a home for Nazi occultism.

The snowbirds here are circus sideshow performers.

Former villa and estate of James Deering developed to preserve native tropical forests.

One-time winter retreats of prolific inventor Thomas Edison and his friend Henry Ford.

Where monkeys run wild and the humans are caged.

The world's brightest bioluminescent bay.

One of seven Jewish catacombs in Rome and one of only two open to the public.

The world’s first penitentiary, meant to be humane, drove men insane.

The prototype for all Nazi concentration camps.

The final resting place for the remains of 143 Habsburg royalty.

A community of collapsing homes more than a mile out from the Florida coast.

Crumbling remnant of Rio's colonial past tucked behind Corcovado mountain in the neighborhood of Cosme Velho.

Beautiful public park off the beaten path and away from tourists.

One of many gator theme parks, abandoned in the sugar fields of South Florida.

A tribute to Ponce de Leon's supposed quest for eternal youth.

Genesis of modern hydroelectric power.

White llama terraces dazzle in Peru's "other Machu Picchu."

The American rainmaker and a burst dam.

Medieval torture techniques with a modern conscience.

Huge masonic hall in Philadelphia with lavishly themed rooms.

Over 50 exquisite hand-painted Renaissance maps decorate a Medici storage room.