This forest city was founded in the 9th century and has a unique plan of stone pathways, plazas, and houses.

A five-day trek to Ciudad Perdida is an adventure by itself, meeting the indigenous Kogi and Wiwa people, who are some of the modern-day guardians.

In 79 C.E., ash from Mount Vesuvius covered and buried Pompeii and Herculaneum for nearly 17 centuries.

Taking a walk through the cities, which are about a 20-minute drive apart, to see frescoes, visit the ancient brothel, see the petrified bodies and the Temple of Apollo.

Excavations of the site on Crete began in 1900.

Travelers can view the remains of the Minoan palace at Knossos. The palace's east wing is adorned with a fresco that depicts three figures and a giant vaulting bull.

Residents abandoned the site with its stone pyramids in the 11th century.

Rediscovered in 1938, it's architectural achievements are impressive: Caana, the temple complex at the heart of Caracol, remains the tallest structure in the country at 141 feet.

Machu Picchu was a sanctuary for the Inca before the fall of the Inca Empire in the 16th century.

The remnant fortifications were rediscovered in 1911. Journey to Machu Picchu, then trek to the neighboring peak of Huayna Picchu for views across the main site.

Troy has a 4,000-year history. Archeologist Heinrich Schliemann used Homer's Iliad like a treasure map and found the site in 1870.

Troves the ancient fortifications and palaces once held are available for viewing in the Troy museum.

Ubar was a trading post deep in the desert. It was lost to the blowing sand for nearly 1,000 years and found in 1992 using images taken from space.

Ubar is located on the southernmost edge of Oman, two hours inland from the Arabian Sea city of Salalah.

Xanadu was a city of the Mongolian and Han cultures, where Kublai Khan ruled.

It is located about five hours northwest of Beijing. Travelers can visit the remains of the excavated temples, stone walls, and tombs of that cosmopolitan capital.

The ancient Maya city of El Mirador, which dates back to 1,000 B.C.E., will only be reached by the adventurous few.

There are two ways to get there: A helicopter or trek two days from the road's end at the village of Carmelita. Once there, you can climb La Danta, a towering pyramid.