Ascents of the mountains were conceived of as metaphorical ascents on the path of spiritual enlightenment, with each stage in the climb representing a stage in the passage through the realms of existence formulated by Buddhism. Buddhist temples were increasingly built on the sides and summits of many Shinto sacred mountains. It was believed that the native Shinto kami of these mountains were in reality manifestations of Buddhist divinities thus pilgrimage to the mountains was believed to bring favors from both the Shinto and Buddhist divinities simultaneously. By the middle of the Heian period the complex interaction of Sangaku shinko, Shintoism and Shingon Buddhism had given rise to one of the most unique and fascinating religious practices found anywhere in the world. This was the sanctification of enormous, yet precisely delineated regions of the countryside through the process of mandalization.
Mandalas have various definitions and uses in different Buddhist contexts.
In Shingon Buddhism they may be generally explained as graphically drawn, symbolic representations of the residence of the Buddha, which is simultaneously the fundamental essence and nature of the human heart-mind. Practitioners of Shingon would utilize mandalas as aids to meditation. By visually entering into the mandala, invoking the deities there represented, and proceeding to the center, the meditator would take one more step along the path towards the attainment of Buddhahood. What is unique to the sect of Shingon Buddhism was its overlay of mandalas onto large tracts of land in order to delimit a grand scheme of sacred areas. The act of going on pilgrimage to the many sacred mountains contained within the great land mandalas, particularly the Kumano mandalas of the Kii peninsula, thus became a profound exercise in spiritual awakening.