This unreal Portuguese palace looks as though it's made from a pile of different castles.

After the owner of this Art Nouveau home died, it was turned into a museum displaying a lifetime dedicated to art.

The medieval castle built as headquarters for the Pope's secretive Knights Templar.

A naturally occurring amphitheater carved by erosion into the mountainside.

This peak in Chapada Diamantina National Park offers the most stunning sunsets.

Deep below the dry landscape of Bahia, a cave with intense blue water to float in.

A submerged village appears when dam levels drop.

This humble bench is considered the most beautiful in the world.

Caves famous for the dragon-slaying saint who lived there.

The largest underground lake in Europe.

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

Italian director Pier Paolo Pasolini fell in love with this lonely 13th-century tower while making his most famous film.

Was this cave created by Hercules's wrath, the devil, or volcanic activity?

The remains of a town so thoroughly destroyed by French forces that the citizens simply left.

This abandoned Brutalist treehouse is a hidden architectural relic.

This Italian stadium makes liberal use of fascist statuary to evoke classical sporting arenas.

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 curious, round temple is the oldest still-standing marble building in Rome.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

Ever hear of the Milazzo Cage?

Hundreds of lucky felines haunt the ruins where Caesar was murdered.

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

A forgotten "city of water" underneath the famous Trevi district.

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