This is indeed the pillar of Heaven, where a hundred rivers meet—
The Earth’s great axis, in ten thousand kalpas unchanged (Wu & Yu, 2012, p. 101).
Eliade (1959) notes that “communication [between heaven, earth, and the underworld in world religions] is sometimes expressed through the image of a universal pillar, axis mundi, which at once connects and supports heaven and earth” (p. 36).
Why is this important? Because the novel describes how Monkey was born from a stone that “had been nourished for a long period by the seeds of heaven and earth and by the essences of the sun and moon” (Wu & Yu, 2012, p. 101). As a pillar of heaven, the height of Flower Fruit Mountain positions the boulder where heaven meets earth, allowing there to be a passage of energies between the two plains of existence through the stone, like electricity through a fuse. This might explain why Sun is so powerful.
Fig. 1- A complex diagram of Mount Sumeru and the associated heavens above and hells below it. If this portrayed Flower Fruit Mountain, Sun Wukong’s boulder would have been located where the summit meets the first heaven (larger version).
As I explain here, the author of Journey to the West supplanted traditional Buddhist geography by placing China in the Southern Jambudvipa Continent and moving India to Western Godinyia. So by making Flower Fruit Mountain the axis mundi, it supplants Mount Sumeru as the center of the cosmos (fig. 1). Admittedly, there is a discrepancy between the literary narrative and the religious cosmology since the book states Flower Fruit Mountain is located “at the border of the small Aolai Country [傲來國], which lies to the east of the East Purvavideha Continent [東勝神洲]” (Wu & Yu, 2012, p. 102). By definition, the mountain can’t be in the center of the world if it’s located to the east of the easternmost continent.
But discrepancies are bound to arise when you tell and augment a story cycle for hundreds of years. Flower Fruit Mountain is mentioned in the 13th-century precursor to the Journey to the West titled The Story of How the Monk Tripitaka of the Great Country of T’ang Brought Back the Sūtras (see Wivell, 1994).
Eliade, M. (1959). The Sacred and the Profane: The Nature of Religion (W. R. Trask, Trans.). New York: Harcourt, Brace & World.
Wivell, C.S. (1994). The Story of How the Monk Tripitaka of the Great Country of T’ang Brought Back the Sūtras. In V. Mair (Ed.), The Columbia Anthology of Traditional Chinese Literature (pp. 1181-1207). New York: Columbia University Press.
Wu, C., & Yu, A. C. (2012). The Journey to the West (Vol. 1). Chicago, Illinois: University of Chicago Press.