Oddee has a neat article titled "10 Most Amazing Lost Cities." On the left is Machu Picchu, which translates to "Old Peak," a pre-Colombian Inca city built almost 600 years ago and abandoned shortly afterwards:
Machu Picchu is probably the most familiar symbol of the Inca Empire. It is often referred to as "The Lost City of the Incas". The site was designated as a World Heritage Site in 1983 when it was described as "an absolute masterpiece of architecture and a unique testimony to the Inca civilization".
Machu Picchu was constructed around 1450, at the height of the Inca empire, and was abandoned less than 100 years later, as the empire collapsed under Spanish conquest. Although the citadel is located only about 50 miles from Cusco, the Inca capital, it was never found and destroyed by the Spanish, as were many other Inca sites. Over the centuries, the surrounding jungle grew to enshroud the site, and few knew of its existence. In 1911, Yale historian and explorer Hiram Bingham brought the "lost" city to the world's attention. Bingham and others hypothesized that the citadel was the traditional birthplace of the Inca people or the spiritual center of the "virgins of the sun," while curators of a recent exhibit have speculated that Machu Picchu was a royal retreat.
Link - Thanks becky!