Before entering into a detailed discussion of the construction of the Temple of the Sun, it is necessary to brush aside the veil of ignorance which until now has covered the purpose of its construction and its importance for the life, economy and religion of the people of that distant period.
As is well known, the great Andean population and that of the nearby regions, was composed in the greater part of farmers and herdsmen (there also existed tribes which devoted themselves exclusively to fishing), and Tihuanacu was the religious and cultural nucleus. The population was extremely dense, as serious studies in this respect show.

Thus it resulted that the agricultural and cattle production of a relatively small region had to provide the support for considerable masses of individuals and so the country was cultivated in an intense way, as we shall see farther on. A bad agricultural year brought famine, discontent, social disturbances and the consequent discredit of the dominant castes. It is also known, even by the person most ignorant of agronomy, that to obtain good harvests and abundant issue in cattle, an exact knowledge of the calendar is necessary. The different seasons and the right times for plowing the fields must be determined, as well as the corresponding seasons for the sowing of certain crops, and the exact moment for breeding various types of cattle.

Of course, the man who is a product of modern culture, and who has an almanac, can scarcely appreciate the importance in that epoch, of possessing exact calendarian knowledge. In order to obtain this data, it was necessary for the castes who ruled the people, to obtain an exact astronomical knowledge, and consequently this science played a highly important role in the most civilized zone of the continent even in that distant period. The great Altiplano, locked between the Andes, was covered then to a great extent by water from which protruded extensive islands and peninsulas. The smallest span of land was utilized by means of "agricultural terraces".

Consequently, the observation of the phenomena which took place in the firmament, especially certain knowledge about celestial mechanics, was indispensable for the Khollas, the sacerdotal caste, in order to provide their subjects with good crops and, as a result, social tranquility and the prestige necessary for the fulfillment of their mission. Consequently, astronomy had not only a religious, but also an essentially practical and social basis. The priests or "Willkas", as they were certainly called, wielded over their subjects, those sail half-savage hordes, spiritual and divine power in addition to their earthly authority. It was thus necessary for them to indicate, not only such agricultural dates as were necessary for irrigation, the breeding of animals, fishing, etc., but also those of the many feast days connected with the seasons and subdivisions of the year.

With the aid of this brief introduction, it will be appreciated that Kalasasaya was something more important than a simple temple of the Sun; it was an Almanac of carved stone, as we shall see farther on, with which there were determined, in a mathematical manner, the different seasons and subdivisions of the year. THESE CALCULATIONS WERE ONLY POSSIBLE BY MEANS OF A BUILDING LOCATED EXACTLY ON THE MERIDIAN AND THE LENGTH AND WIDTH OF WHICH CONFORMED TO THE MAXIMUM ANGLE OF SOLAR DECLINATION BETWEEN THE TWO SOLSTICES.