Haunted by its violent past, this colonial bastion was the largest Spanish military installation in the Americas.

This 16th-century monastery was founded to cloister the daughters of wealthy local families.

Built on the remains of one the Incas’ most important gathering spots, this square keeps the spirit of a fallen empire alive.

This geometric feat is a testament to the Incas' mesmerizing architectural abilities.

Situated on a sacred Inca site, this 16th-century cathedral took nearly 100 years to build.

The mysterious "Candelabra of the Andes" could represent anything from a god's trident to a hallucinogenic plant.

The remains of what was the most important religious complex in coastal Peru for over a millennium.

This Peruvian canyon is filled with geometric salt pools that have been being harvested since the Incan empire.

The stones of this Incan wall complex fit together so well you couldn't fit a piece of paper between some of them.

If you’ve ever seen a picture of Machu Picchu, then you’ve seen a picture of Huayna Picchu—you just didn’t realize it.

Huge stone depressions which may have acted as an Incan agricultural experiment.

An unexpected desert oasis in South America.

Preserved Inca city and site of the last Inca stronghold against the Spanish conquistadors.

The intricate stonework of Machu Picchu serves as a testament to Incan engineers.

A brutalist gem towering over the heart of Milan.

Two very green residential towers cleaning the air in one of Europe's most polluted cities.

An ossuary built in 1210 to collect bones from the Ospedale Maggiore of Milan.

A special area of the National Archaeological Museum of Naples is located inside a metro station.

This medieval city gate is now a blend of the past and the modern world.

San Gennaro, the patron saint of Naples, greets pedestrians between these narrow city streets.

Every day is like Christmas on this street where the traditional Neapolitan nativity scene comes to life.

In a city that boasts four separate inclined cable railways, this is one of the busiest funicular lines in the world.

The Neapolitan Cult of the Dead still cares for the skulls at this mini-Fontanelle.

Dug as a secret royal escape route, the tunnel became a wartime bomb shelter and dumping ground for vintage cars.