Renaissance hospital featuring a rotating door into which unwanted babies were dropped.

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

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

This small, ancient Roman temple was once a church dedicated to the patron saint of penitents.

This ancient market is often referred to as the oldest shopping mall in the world.

Museum dedicated to literary greats of the Romantic Period is also the home in which Keats met his untimely end.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

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

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

The crypts of Capuchin friars decorated with the bones of over 4,000 friars, including an entire "crypt of pelvises."

Ugly 18th-century dwarf statues living in a perfectly landscaped Austrian garden.

The topiary maze at the Habsburg hunting lodge.

Old ships and machinery fill a historic harbor in the city that's home to Europe's largest port.

An early 19th-century English style garden hidden in the Rotterdam cityscape.

This massive mural by famed pop-artist Keith Haring was hidden for almost 30 years until its 2018 rediscovery.

Birthplace of the "Cat in the Cradle" and a cluster of iconic, original windmills that let the Dutch tame the seas.

The site where one of the most famous poems of World War I was composed is preserved to honor the legacy of the work.

A little sculpture with a large wardrobe.

Climb inside an iron crystal magnified 165 billion times its normal size.

The 20th-century chapel’s intricate woodwork includes amazing details, most notably angels playing bagpipes.

This alley off Edinburgh's Royal Mile contains remnants of the city's seedier history.

Touching this 18th-century Scottish philosopher’s toe allegedly conjures good fortune.

The most loyal of little dogs, or a Victorian era publicity stunt?

A beautiful Greco-Roman structure houses a well once believed to have healing powers.