Go inside to really appreciate this 500-year-old technological masterpiece.

This palatial spiral staircase was so unusual the name "snail" was given to the noble family who built it.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

Caligula's colossal pleasure ships, discovered by Mussolini only to be lost in flames.

A modern sliver of architecture in Roma.

2300-year-old Roman road connecting the empire.

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

This seaside Italian village doesn't just look Escher-esque, it actually inspired the mind-bending artist.

One of the world’s smallest bars, just 13 square feet, is brimming with speakeasy flair.

The artist and his brother are buried in a landscape straight out of a van Gogh painting.

The mummified heart of Louis XVII, the lost dauphin of the French Revolution.

Got apples?

France's most famous cemetery, with some of its most curious tombs.

Twelve grave-faced marble angels guard the emperor's tomb at Les Invalides.

A favorite Paris bar for U.S. expats, including Gershwin, Hemingway, and James Bond.

The spiral staircase hidden inside this giant Parisian column was likely built for Catherine de Medici's astrologer.

A curious collection of locks and keys.

"In the Dark" Restaurant in Paris offers dinner in complete darkness.