19th-century scientists would make the pilgrimage here to verify the precision of their measuring sticks.

Northern Ireland's Brobdingnagian stepping stones.

Breathtaking and huge 430 year old maps of Italy.

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

The studio built by fascists in the hopes of "reviving the film industry" with the occasional propaganda film opportunity thrown in.

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

2300-year-old Roman road connecting the empire.

Tourists to the mountaintop Sicilian town often overlook its ancient fortifications.

A secret hatch containing two parchments was discovered in this statue over 40 years after its installation.

This breathtaking monastery was established by Saint Benedict himself 1,500 years ago.

The walls and streets of the ancient city are peppered with penises.

Erotic art covers the walls of the largest ancient pleasure palace.

The world's most active stratovolcano is almost always erupting.

Ancient snack bar of the Roman Empire re-opened.

A master of trompe-l'oeil creates a stunning, tourist-fooling dome out of a flat ceiling.

Originally used to sell brandy, the bull-shaped billboard became an iconic symbol of Spain.

The world's most elegant power lines.

An abandoned airport in the middle of nowhere.

Spanish architects used seized Muslim gravestones to rebuild parts of the fortress.

One of the most spectacular bridges in Spain spans a narrow chasm that divides the city of Ronda.

Rare karst landscape eroded from a flat seabed.

Three bridges and one giant canyon make up this fantastic Spanish settlement.

This abandoned Greek island was the last active leper colony in Europe.

This famous archeological mystery may be an ancient example of movable type.