The head of Serpent Mound aligns with the point on the western horizon where the sun sets on the summer solstice, the longest day of the year. Some interpret the serpent’s three main body curves as pointing to the summer solstice sunrise, the equinox sunrise, and the winter solstice sunrise. Others believe the alignments instead relate to the moon, including the minimum northern moonrise at the midpoint of its cycle and the maximum southern moonrise. Because the sight lines are short and the U-shaped curves of the mound do not allow precise alignments to be defined, it may not be possible to determine whether the builders intended the Serpent to align with the sun or the moon. Many earthworks created by the ancestors of contemporary American Indians align to horizon points marking important rising and setting points for the sun and moon, possibly linking sacred sites to cosmic rhythms or allowing them to serve as calendars.