In Inca mythology, Uku Pacha was defined as the world below, which was the world of the dead, of the unborn and of everything that was under the terrestrial or aquatic surface. The sources (in Quechua, Pukyu), caves and any opening in the earth's crust were considered as a means of communication between Uku Pacha and Kay Pacha.
The world was composed of four planes, Hakaq Pacha (world beyond), Hanan Pacha (the world above), Kay Pacha (the world here) and Uku Pacha. In practice there used to be in the Tahuantinsuyu a complementary dualistic "division" quite similar in some respects to the Chinese yin-yang between the Hanan and the Urin (or Uku) that came to the point of qualifying some Hanan populations ("superiors"). ") and others of" inferiors "(Urin, Uku) understanding them as complementary, although unlike the Chinese complementary dualism it is not clear if the division between Hanan / Urin or Uku implied a reciprocal and progressive passage from the Hanan (the superior, the solar, the virile etc.) to a Uku or Urin (the low, the dark, the feminine) and thus in cycles.
In the Quechua language, pacha meant both time and space, although the most usual meaning is land. For example, when the pachamama is honored, a fertility rite is performed, so that the earth may bear fruit in exchange for the offerings and other sacrifices.
The animal representation of Uku Pacha was represented by a giant serpent or snake Amaru.
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