Geometry and mystery come together in an epic show of octagonal masonry.

A fortified medieval basilica on the Caelian Hill preserves extraordinary frescoes and one of Rome's most beautiful hidden cloisters.

A medieval stronghold rising over the ruins of ancient Roman villas along Rome's southern coast.

This beautiful park on the outskirts of Rome protects the ruins of two colossal ancient aqueducts.

This enormous sinkhole hides a secret world created from divine wrath.

A 17th-century doorway in a small Sabine village is a portal into the mysteries of alchemy.

Magnificent frescoes decorate the interior of this Romanesque church, which also showcases an unusual phenomenon during winter solstice.

Naturally preserved bodies are eerily staged throughout the crypt in varying poses.

A nearly 100-year-old dining car in upstate New York embodies the golden age of roadside dining.

A tiny chapel clings to a precipice above Germany’s gemstone capital.

Italy's curious field of mud volcanoes is named for being both gross AND salty.

A collection of objects supposedly singed by the hands of souls in purgatory.

Hidden in an Italian forest is a completely homemade amusement park that has taken a lifetime to create.

An unusual sculpture with a meaning shrouded in mystery.

A gorgeous medieval library where the books are kept in chains.

A domed disco abandoned since the '70s now attracts artists and explorers under its unique roof.

A medieval, mosaic-lined baptistry built by a heretical Christian sect.

Filled with goldfish swimming in a shallow pool of sea water, this ancient crypt is more wishing well than burial site.

An incredible mosaic-lined monument said to have held the remains of an ancient Roman empress.

Psychoanalyst Carl Jung reported a paranormal experience after visiting this mosaic-lined Roman baptistry.

This ultra-modern burial building would have stacked the dead like a giant filing cabinet.

David Sedaris called it "The greatest shop in the world."

This medieval Italian village was transformed into an architectural marvel by the famous "Papessa" Donna Olimpia.

This ancient altar emerges from the thick forests to reveal the mysteries of Etruscan sacrificial rituals.