'The palace' in the sentence which read, 'Walls were built by piling stones on the mountain to the east of the palace,' mentioned in Nihonshoki means the ruins of Asukakyo and 'the mountain to the east (of the palace)' is the hill on which Sakefuneishi is located.
記述中の「宮の東の山に石を累ねて垣とす。」の「宮」が酒船石の南西にある飛鳥京跡であり「東の山」が酒船石のある丘ということである。