Architectural monsters are devouring this palace's every door and window.

This hidden Art Nouveau courtyard is an opulent feast for the eyes.

2300-year-old Roman road connecting the empire.

The final resting place of the poets Shelley and Keats.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

This massive library holds what was once the largest book collection in the world.

In the best of all possible worlds, everyone will get a chance to see this statue in which Voltaire's heart is interred.

A 400-year-old church covered floor to ceiling in ex-voto offerings from the faithful.

Indents in the pavement are all that remain from a grisly death machine in Paris.

This impressive collection of rare books on ancient mysticism inspired author Dan Brown.

An ancient passage filled with stalls selling used books, once frequented by Vincent Van Gogh.

A Dutch passageway's artistic, aquatic-themed makeover pays tribute to the capital city's famed waterways.

A hidden church in a hidden courtyard tells the story of the Miracle of Amsterdam.

The oldest still-existing mosque in the United States sits in a remote prairie in North Dakota.

A monument to the center of the North American continent may be off by a few miles.

This Bordeaux parking garage has 712 indoor spaces, and one outdoor.

An intricately designed junk art house with four extravagant junk art cars hidden in the suburbs.

A floating underwater hotel, created by a Swedish artist.

Sleep in a glass pod dangling off a cliff.