Serpent Mound has been compared to the ancient observatory at Stonehenge.  In an earlier version of Serpent Mound Mysteries, Ross Hamilton wrote "Physically set apart by the great Atlantic Ocean, the planning of these two prehistoric sites seems to be unified in the essentials of a common, naturally disciplined school of architecture. This "school," for want of a better definition, can be viewed as the logical and practical school. The specific juxtaposition of the Great Serpent with Stonehenge—applying first astronomical, geometrical, and then numerical guidelines—reveals that the two monuments appear to have been designed together as part of a larger picture." (Hamilton, 2001)  Some of his writings are available as archived material.