A 2,000-year-old engineering wonder hides beneath an Italian town.

This abandoned Brutalist treehouse is a hidden architectural relic.

The ruins of a hermitage constructed during the 12th century.

This 16th-century monastery has been turned into a surrealist architecture compound.

A lonesome Moai stands in a small Italian town some 9,000 miles away from its Easter Island brethren.

This Parisian fountain is a little bit fantasy and a little bit nightclub.

This charming cobbled backstreet is the most Instagramable street in Paris, much to the residents' annoyance.

A museum of magic with a Sadist past.

This frog-themed restaurant was frequented by Picasso, Saint-Exupéry, and more.

A counter-culture bookstore like no other hides in plain sight in the streets of Paris.

Notorious artist squat renovated into legal studios.

The oldest stone house in Paris was built by its most famous alchemist.

This banal Parisian entranceway is not what it seems.

Drink wine handed out through a window as part of an age-old tradition.

Nestled in the hills of Tuscany are gorgeous, multicolored hot springs.

Stumbling upon this whimsical wooded garden is like stepping into an enchanted forest full of philosophical musings.

Nine caves filled with recently-discovered archaeological finds under the houses and the streets of the most ancient district of an old town.

This picturesque Umbrian city has a subterranean side that has long remained hidden.

Water and windows define this defensive Italian well.

A magnificent Neogothic tomb hides within this Italian fairytale-like forest.