A sulfuric hellscape in southern Italy.

A statue representing a lost Roman profession that was vandalized for centuries.

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

Architectural monsters are devouring this palace's every door and window.

More sculpture than building, this architecturally significant temple was built on the spot of Saint Peter's crucifixion.

Brass cobblestones mark the places where individual Holocaust victims were taken from their homes.

This ancient market is often referred to as the oldest shopping mall in the world.

Rome's semi-secret peephole vista is also a former Crusader stronghold.

This ancient Roman prison is decorated with an upside-down cross not as blasphemy but as saintly tribute.

A 15th-century monumental Latin inscription on this house celebrates Lorenzo Manilio's love for Rome.

In Rome’s Jewish ghetto, a 200-year-old bakery still makes the neighborhood’s historic sweets.

This is the oldest Roman-made bridge in the city still existing in its original state.

In the early Roman Empire, people deemed traitors and criminals were tossed to their deaths from this rock.

A rare example of a medieval house in Rome adorned with a melancholic inscription.

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

The underground sanctuary of a mysterious ancient cult.

An ancient stone structure that, according to legend, was built by witches.

This 17th-century passageway is home to numerous bookshops, a witch legend, and the oldest pizzeria in the world.

Hidden under a center for the elderly are the dungeons which were used during the Spanish Inquisition.

This Arab fortress was once the largest citadel in Western Europe.

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

One of the largest and oldest caravansaries in Persia.

In this tiny Iranian town playing on the roof isn't just encouraged, it's the only place to go.

This ruined fortress was the stronghold for a persecuted medieval leader and his infamous Assassins.