The Cheon’gae-seok/天蓋石 stone, which is placed almost like a cover stone at the center of the ceiling of the Seokgul-am dome, is cracked and therefore feature three portions. According to the tales featured inside Samguk Yusa, which mention the construction of Seokgul-am, the stone which was to be lifted and used as the ceiling stone was cracked in mid-construction, yet while Kim Dae Seong, chief supervisor of the Seokgul-am construction, was in sleep, a god of heaven came and lifted the cracked stone to the ceiling. Many researchers estimate that the stone should be around 2.5 meters in diameter, and weighs roughly 20 tons, and they are most interested to find out how such a large stone, and not to mention in a cracked status, could have been positioned at the center of a dome's ceiling. They have been in search for the technique which would have enabled such positioning, and they are anxious to know the reason why the stone was not replaced with another stone that was not cracked. Some people believe that it was the technicians who lifted the cracked stone while Kim Dae Seong was asleep, yet Kim did not oppose it and have it removed because he also dreamt of a god of heaven visiting and lifting the stone. Other people present another possibility that a wise intellect, described in the tale as a god from heaven, might have argued that the fact the stone was cracked in mid-transport symbolized the really difficult nature of unifying the three dynasties, and that person might also have suggested that the stone be used without being replaced. And others simply believe that the Shilla technicians as a habit did not conclude their job very cleanly, and were actually content to place a cracked stone at the ceiling. Such previous opinions were based upon a belief that the tale was containing historical truth, and in that regard they are all misguided. Tales in nature, are told by people who would like to determine the causes to a certain condition of a vestige or an artifact, and then simply decide to come up with theories based upon evidences that they did not actually witness with their own eyes. A god of heaven could not have lifted that stone, so we can safely come to the conclusion that this tale is quite evidently not based upon an eye-witness account to the actual construction process. It is a mere speculation accumulated by people who gathered at Seokgul-am, happening to be talking about how such a heavy stone piece would have been placed at the center of a dome's ceiling. Rational presumptions can be made. The major earthquake that hit the Gyeongju area in 779, or the major flooding that engulfed the Eastern region of Shilla in 797, two catastrophes that took place only a few years or one or two decades after the construction of Seokgul-am was complete, could have been the reason for the crack. The stone was at the center of the dome's ceiling, so it was very much vulnerable to being damaged by either the shockwave from a quake, or simply the additional weight of accumulated dust piled upon the ceiling. People of the past who visited the grand beauty that was Seokgul-am, would have been in awe of the sheer magnificence of all the Buddhist images and not to mention the internal structure of Seokgul-am itself, so some of them were bound to interpret the cracks in the ceiling as a result of some intentional designing, and to create stories of their own, containing mystical properties. The approach featured in this article could contribute to future tasks dedicated to determining the validity of tale materials, and not to mention raising the level of public understanding of the internal structure of Seokgul-am, one of the proud legacies of the Korean people even acknowledged from global standards. The unfair evaluation of the Shilla technicians could also be corrected.