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

A subterranean relic of the Spanish Civil War hides below this picturesque park.

These abandoned Cold War-era bunkers are now a designated refuge for endangered bat species.

Fortifications built for a Soviet invasion that never came now sit abandoned in a losing battle against nature.

Although resembling a grand Buddhist temple, this structure is actually the largest mosque in China.

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

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

This ancient Roman bridge was a key feature of the ancient Via Salaria road.

This large, circular tomb is the final resting place of the first emperor of Rome.

This 13th century Gothic brick castle is the largest in the world by surface area.

This magnificent castle grew from a small Moorish fortress, and reportedly inspired two iconic Disney castles.

An ancient Roman temple first dedicated to an emperor's wife is now a church.

Designed as a labyrinth, this subterranean prison was crafted without bars or doors.

The ruins of this medieval castle overlook the lake of Piediluco in what was once a sacred forest.

The 20th-century archaeologist was interred among the ruins of an ancient Roman city.

The Roman city was the birthplace of various emperors and is home to one of the empire's most impressive architectural feats.

Once the grandest synagogue in medieval Spain, it now stands as a memorial of the 15th-century Jewish exile.

The ruins of an ancient stadium that hosted gripping chariot and horse races.

There are two legends behind the origin of this unusually tall sanitary structure.

The fragmented remains of a massive public bath connected to the city's water supply.

This seventh-century fortification marked the western border of the Lombard duchy of Spoleto.

A secluded fortress from the days of the Crusades that offers breathtaking views.

A crumbling watchtower and a lighthouse overlooks the site believed to be the Sirens' cliff in the "Odyssey."

A single column facing the sea is all that's left of one of the most important temples of Magna Graecia.