Green Castle Hill is situated on the northern fringe of the volcanic highlands and the Central Plain Formation of Antigua. The hill provides a strategic view of the west coast and triangular shaped isolated hills of the Central Plain.
On the summit and slopes of this hill, are unusual standing rock formations referred to by Antiguans as megaliths. Although the origins of these standing rocks remain an issue of speculation and mystery, they are clearly associated with a pre-Columbian site. The site is delineated by the remains of shellfish, pottery, lithic flakes and debitage, and faunal remains.
It has long been speculated that the hilltop may have been used for ritualistic functions, such or observing the night sky; an ancient observatory. Recent astronomical surveys support this speculation.