The Thracian religion refers to the mythology, ritual practices and beliefs of the Thracians, a collection of closely related ancient Indo-European peoples who inhabited eastern and southeastern Europe and northwestern Anatolia throughout antiquity and who included the Thracians proper, the Getae, the Dacians, and the Bithynians. The Thracians themselves did not leave an extensive written corpus of their mythology and rituals, but information about their beliefs is nevertheless available through epigraphic and iconographic sources, as well as through ancient Greek writings. Origin The Thracian religion, and especially its creation myth and its pantheon, were derived from the Proto-Indo-European religion. The Thracian conceptualisation of the world, which held that it was composed of the four elements (Air, Earth, Fire, Water), is attested from the early Bronze Age, around the fourth millennium BCE, and was recorded in poems and hymns originally composed in the late Bronze Age during the 2nd millennium BC which were later passed down orally. By the end of the Bronze Age, the cult of the Sun was prevalent throughout Thrace. Daily use objects and art were decorated with symbols of the Sun, and the representations of the Sun were carved into cliffs and in the rocks of the eastern Rhodope Mountains. The late Bronze Age was also a period during which there were considerable cultural contacts between Thrace, northern Greece and Asia Minor. This cultural contact led to significant religious exchanges, such as the importation of the belief in the Great Mother Goddess in Thrace. Accompanying the spread of the belief in the Great Mother Goddess to Thrace was the evolution of the concept of the divinisation of the mountain in the later 2nd millennium BC and the early 1st millennium BC, which was itself contemporaneous with the flourishing of megalithic culture in Thrace. Remains of this megalithic culture include many monuments, such as rock-cut niches of rectangular or circular of trapezoidal shape for votive gifts, platforms for sacrifices which include troughs and drainage outlets for the victims' blood, sacred steps to springs or rock sanctuaries, complexes of megalithic structures, and dolmens. During the late Bronze Age and the early Iron Age, the cult of the chthonic deity Zagreus (Dionysus) also spread across the Hellespont from Anatolia into Thrace during a period of social crisis in the Balkans peninsula, and from there it spread into Greece. Although the cult of Zagreus was initially opposed by the practitioners of