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

The glowing blue Nymphaeum of Emperor Tiberius.

Sitting on an Italian hilltop is this surreal fortress built by the mad inventor of electrohomeopathy.

Geothermal waterfalls in Tuscany.

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

Stalactites and stalagmites in a beautifully lit cave.

The underground sanctuary of a mysterious ancient cult.

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

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

A small stone monument marks the spot on Stavely Road where the first of hundreds of missiles touched down during World War II.

This plaque in one of London's oldest public hospitals commemorates the first meeting of two of Britain's most famous literary heroes: Sherlock Holmes and Dr. Watson.

Heralded as the oldest statue in London.

Above an abandoned Underground station, this charming bookstore is home to strange antiquities and literary works.

Where Aleister Crowley attempted to seize the Hermetic Order of the Golden Dawn in a mask and a kilt.

A Roman spa buried deep beneath the City of London.