This Industrial Age architectural and engineering gem helps visitors and residents alike traverse Lisbon, “The City of Seven Hills.”

The last moments of the ill-fated Pompeiians, frozen forever in plaster.

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

Ancient snack bar of the Roman Empire re-opened.

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

A sulfuric hellscape in southern Italy.

The glowing blue Nymphaeum of Emperor Tiberius.

This remarkably well-preserved Egyptian plinth is pretty well traveled for a giant piece of stone.

Ancient serpentine sacrifice holder that has stood the test of time.

A marvel of Byzantine engineering under the streets of Istanbul.

This legendary city has been a tourist attraction for centuries.

This ancient Greek place of assembly and marketplace is being revealed layer by layer below the modern Athens cityscape.

The hallucinogenic center of the ancient world.

The former Nazi Germany concentration camp stands as a museum to remember this dark chapter in European history.

An underground city of salt.

This Polish cave has housed a dragon, a brothel, and an enduring legend.

A restaurant and observation deck built in a unique broadcasting antenna.

The site of a concentration camp where inmates were made to take part in one of the largest counterfeiting operations in history is now hauntingly empty.

Human-made caves excavated to hide a secret society of wealthy pagans.

Luxurious hotel designed to stir the imagination of its many visitors.