Although the amount of arable land which could be made available with the most careful terracing was not large enough to support a very great population, Machu Picchu offered an impregnable citadel to the chiefs and priests and their handful of followers who were obliged to flee from the rich plains near Cuzco and the broad, pleasant valley of Yucay.  Only dire necessity and terror could have forced a people which had reached such a stage in engineering, architecture, and agriculture, to leave hospitable valleys and tablelands for rugged canyons.  Certainly there is no part of the Andes less fitted by nature to meet the requirements of an agricultural folk, unless their chief need was a safe refuge and retreat.

Here the wise remnant of the Amautas ultimately developed great ability.  In the face of tremendous natural obstacles they utilized their ancient craft to wrest a living from the soil.  Hemmed in between the savages of the Amazon jungles below and their enemies on the plateau above, they must have carried on border warfare for generations.  Aided by the temperate climate in which they lived, and the ability to secure a wide variety of food within a few hours’ climb up or down from their towns and cities, they became a hardy, vigorous tribe which in the course of time burst its boundaries, fought its way back to the rich Cuzco Valley, overthrew the descendants of the ancient invaders and established, with Cuzco as a capital, the Empire of the Incas.

After the first Inca, Manco Ccapac, had established himself in Cuzco, what more natural than that he should have built a fine temple in honor of his ancestors.  Ancestor worship was common to the Incas, and nothing would have been more reasonable than the construction of the Temple of the Three Windows.  As the Incas grew in power and extended their rule over the ancient empire of the Cuzco Amautas from whom they traced their descent, superstitious regard would have led them to establish their chief temples and palaces in the city of Cuzco itself.  There was no longer any necessity to maintain the citadel of Tampu-tocco.  It was probably deserted, while Cuzco grew and the Inca Empire flourished.

As the Incas increased in power they invented various myths to account for their origin.  One of these traced their ancestry to the islands of Lake Titicaca.  Finally the very location of Manco Ccapac’s birthplace was forgotten by the common people—­although undoubtedly known to the priests and those who preserved the most sacred secrets of the Incas.

Then came Pizarro and the bigoted conquistadores.  The native chiefs faced the necessity of saving whatever was possible of the ancient religion.  The Spaniards coveted gold and silver.  The most precious possessions of the Incas, however, were not images and utensils, but the sacred Virgins of the Sun, who, like the Vestal Virgins of Rome, were from their earliest childhood trained to the service of the great Sun God.