Each night, the moon rises and sets at a slightly different point on the horizon. Over the course of an 18.6-year cycle, the moon follows a path recognized by the people of the Hopewell culture, who encoded it in the Octagon Earthworks. Every 18.6 years, the moon rises in perfect alignment with the main axis of the Octagon Earthworks, marking the moon’s northernmost rise. Ceremonial leaders likely viewed this convergence from the Observatory Mound. The sides and corners of the Octagon also serve as sight lines by which the moon’s passage can be tracked to its maximum northern and southern rises and sets. The moon was an important means of tracking the passage of time and likely held significant spiritual importance.