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

A Christian monastery stands on what was once a holy Incan temple.

These ruined Incan mausoleum towers still bear carvings of sacred animals on their blocks.

The Uros people live on floating reed islands in lake Titicaca.

A set of ancient drawings in the desert of Peru that are so massive, many of them can only be fully seen from the sky.

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

A bit of retro transportation flair preserved in the world's largest department store.

The 28-foot granite map plots the locations of 40 theaters in New York City.

Looking strangely like Rome's Colosseum, this unfinished tower has dominated the skyline for over 100 years.

Overlooked by many, the two famous Scottish warriors guard the main gate of Edinburgh Castle.

The world's largest second-hand graces a clock surrounded by constantly changing flower beds. 

The central mosque of this Mali town is entirely built from mud.

These homes carved into the mountains seem to defy the laws of nature.

Every year, people come together to cover this mud-brick mosque with a fresh layer of earth.

Muammar Gaddafi's well-intentioned investment in his favorite city turned out to be a nightmare.

One of Western Africa's oldest mosques, this Timbuktu icon has stood for nearly 700 years.

Charnel house at the foot of Mount Sinai.

This fortress was built using the last surviving stones from the Lighthouse of Alexandria, one of the Seven Wonders of the Ancient World.

This memorial park is also the original site of Queen Cleopatra’s Caesareum, whose pillars now stand in London and New York.

The lost library of Alexandria, revived as a spearhead of cultural preservation.

In Egypt's expanding metro area, many of the neighbors are dead.

The medieval center of the Islamic world was also once the seat of Saladin's sultanate.

Standing atop 2nd-century Roman ruins, this church is one of the oldest and most iconic in Old Cairo.

This ancient structure is widely thought to be the oldest intact pyramid in the world.