A plaque marks the underground site of one of London's "lost rivers."

It is still illegal to "quarrel" at this unlikely urban oasis built on top of an electrical substation.

This five-star hotel was originally a swanky parking garage.

The site of the notorious Great Train Robbery of £2.6 million, one of the biggest heists in English history.

This high-speed test track is popular with car manufacturers, speed freaks and orbiting astronauts.

A long-buried ancient ruin unearthed right in the middle of the city.

Three underground crypts and a pointed arch under the bell tower make this cathedral unique among Romanesque churches.

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

Skulls and skeletons are omnipresent in this church dedicated to souls trapped in purgatory.

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

Southern Italy's spinning top village.

The sunlight passing through the opening of this huge cave system creates a magical effect.

A dead saint, a deadly poison, and a mysterious holy ooze.

2300-year-old Roman road connecting the empire.

This small Roman arch was transformed into a dwelling by the founder of the Trinitarian Order.

Roman politician Herodes Atticus built this nymphaeum to honor his wife, whom he may have murdered.

A detailed pachyderm supports Rome's smallest Egyptian obelisk.

An alchemist's “magic door” stands in the middle of a Roman park.

This Roman arch marks the location of an ancient gate at one of the Seven Hills of Rome.

The ruins of the largest gladiatorial school in Rome are largely hidden under modern streets.

Architectureal fantasy quarter of Rome.

Keep a lookout for replicas of this wooden soldier hiding in plain sight all around town.

A hill carving of the legendary dragon that terrorized the village of Bures in the Middle Ages.

Long before wi-fi, this public seat provided the wonder of being online while outdoors.