It is a universal characteristic of primitive men that the most enduring and best-constructed buildings are those devoted to worship. We find, for instance, throughout the Old World that the prehistoric structures of this kind which have survived as monuments of the past are temples, either in the form of rude monoliths or imposing buildings, the habitations of their builders having long since disappeared, as they were built of perishable material and their sites can now be detected only by low mounds. Temples, however, were more lasting and work on them was cumulative; each generation improved on its predecessor, and as they were built of stone the additions of successive generations were permanent, and remained as an index of past civilization. The same is true among prehistoric pueblos of North America. They also erected dual buildings: one being a perishable habitation; the other the permanent religious building. Let us consider the chronological evolution of these two types of architecture. In the very earliest condition the primitive people of the Southwest constructed a massive-walled building to serve for the performance of their rites and ceremonies. Each social group had its own sanctuary, which we now recognize as the kiva, commonly built in the form of towers scattered throughout the mountainous regions of Utah and Colorado. As is customary with similar religious edifices, we find these, as a rule, perched on the tops of high cliffs, not for outlooks, but for conspicuous buildings for refuge of the neighboring population. In ancient Greece we find the temples of Cecrops, the ancient deity of Athens, on an Acropolis, and towering above Corinth is the Acrocorinth. Towers almost identical with those of Colorado occur in different localities in Europe. We find them, for example, in Ireland, in Spain, in Sardinia, and in Corsica, where they have received a different name, but are always associated with the very earliest inhabitants of those localities. In Peru we find the problematical _chulpas_. The function of these towers in both the Old and the New World has been a bone of contention among archeologists. The best explanation that has been advanced for Old World towers is that they are defensive and religious structures; the towers of the New World may have had a similar use, as they are alike in form. In other words, we may suppose that they also are religious structures, but we can add in support of that theory evidence not available in Europe, for we find that, the form of the tower is identical with that of the sacred room or kiva, and that it has survived to the present time as a special chamber for worship.