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

Mysterious tombstones thought to be remnants of Atlantis.

A natural arch carved by a river gave its name to the so-called "Cave of Forgotten Dreams."

A former millstone quarry in the Italian Alps is strewn with rocks bearing distinct round shapes.

These ruins on Mont Tantané dates back to the Iron Age, but there is limited evidence for why a village was built so far from water or other resources.

High in the Italian Alps, a lonely chapel with a striking view of the Matterhorn.

Mounds, rune stones, and a 1,000-year-old church, left behind by Denmark's first two kings.

A symbol for the opposition to nuclear power around the world.

Dozens of musicians have planted trees in this Danish park, and donated songs to go with them.

This Danish rock field is actually a sprawling ancient cemetery holding the bodies of 700 Vikings.

For centuries this cliffside aqueduct was believed to be of Roman origin, but it actually dates to the medieval era.

A mysterious ancient elephant said to possess magic powers is now the symbol of a Sicilian city.

The ancient mosaics here are considered among the finest in the world, and serve as a stunning record of Greco-Roman daily life.

The largest caravanserai in Cyprus also includes amazing examples of Ottoman architecture.

An ancient necropolis of magnificent tombs.

A tribute to the incredible generosity the Choctaw Nation showed the Irish people during the Great Famine.

This singular Irish dolmen is more Frank Lloyd Wright than upright stonehenge.

Centuries ago, red and white wine poured from the statue's breasts whenever a new Venetian ruler was elected.

This narrow Ghent alleyway is an officially sanctioned street art tunnel.

A wonderfully kitsch bookstore the size of a supermarket.

Brussels' favorite peeing boy has a sister.

A fantastical 13th-century fortification sandwiched by a modern hotel in central Brussels.

This Greek temple, open only an hour a day, was the site of a war of tastes between an architect and an artist.

A little sculpture with a large wardrobe.