This 4,000-foot-diameter hole is touted as "the most well known, best preserved meteorite crater on Earth."

One of Antoni Gaudí's most classic buildings is well-known for its "dragon-back" design.

Construction of Barcelona's iconic (but controversial) church is expected to be completed in 2026—a century after the death of its architect.

This Venice bookstore has resigned itself to constant flooding by keeping its books in bathtubs and boats.

This weird abode has inspired everything from the "House On Haunted Hil" to a robot hunter's pad.

An ancient capital city that dates back 3,000 years old and harbors many surprises.

Famously misunderstood wonder of the ancient world

The ancient dwellings of the Puebloans, located in the cliffs of majestic mesas.

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

A 16th-century horror show built in a lovely Italian garden.

The engineering wonder and pleasure dome of a much-maligned emperor still holds undiscovered secrets.

Ruins of the Crusaders' headquarters.

Pompeii's less famous neighbor is still revealing her secrets.

This legendary city has been a tourist attraction for centuries.

One of the earliest relics of Italian art is this ornately equipped stone soldier.

The "Greatest Sewer" of ancient Rome is one of the oldest sewer systems in the world, and is still in use.

People have been living in the cave houses on this Italian hillside since the Neolithic era.

One of its engravings is believed to be among the first representations of medical and surgical instruments.

This bustling Italian plaza is built on the ruins of an ancient Roman amphitheater.

The Roman Emperor's lost summer home and grotto full of enormous sculptures sit along the Italian seashore.

This ancient structure is widely thought to be the oldest intact pyramid in the world.

A labyrinth of ancient tunnels hidden below the city holds the ruins of 2,500 years of history.

One man's remarkable private collection of art from around the world.

An ancient octagonal weather station named for the eight Greek gods of wind.