 It sits in ten feet of water on the west end of Greens Ledge, a shallow underwater reef that runs a mile west of Sheffield Island and is roughly a mile south of the entrance to Five Mile River at Rowayton.Completed in 1902 by the Philadelphia Construction Company, the cast iron structure is approximately 90 feet tall including roughly 15 feet of the submerged caisson.In 1933, more than 30,000 tons of rocks from the excavation of Radio City Music Hall were added to the riprap foundation.