MACHU PICCHU: This mountain-ringed Inca sanctuary, never found by the Spanish conquistadors, was "discovered" for the outside world in 1911 by American explorer Hiram Bingham. Remote and legendary, the labyrinthine hilltop complex is the most spectacular archaeological site in South America.

It is believed the citadel was built by the Inca emperor Pachacuti starting in about 1440 and was inhabited until the Spanish Conquest in 1532.

A haunting reminder of the Inca Empire, the site inspires feelings of cosmic harmony - a bridge between past and present. Chilean poet Pablo Neruda, in his classic poem Heights of Machu Picchu, wrote:

Then up the ladder of the earth I climbed
through the barbed thickets of lost jungle
until I reached you Machu Picchu:
High city of laddered stone,
finally resident of what is earthly
you did not hide in the dormant raiment

To call Machu Picchu a ruins does not do it justice. Atop the mountain ridge, 250 houses and temples still stand intact after more than 500 years with walls slanted inward to withstand earthquakes.

As part of the engineering marvel, the Incas constructed an intricate water system of fountains and aqueducts fed by underground springs and made the fortress self-sufficient with terraced outcroppings for farming.