 Sweetser described Long Island as conspicuous by its municipal buildings, and still more by its lighthouse perched on the very tip of the steepest cliff in the harbor, eighty-feet above the high-water mark and visible for fifteen miles (24 km) at sea.The battery, which crowns the cliff, presenting only a range of green mounds to the view of the passing sailor, is a formidable little work, of modern construction, with walls of great thickness, bombproofs, and other defenses, partly separated from the rest of the bluff by a deep dry moat.In 1893 a huge construction project was begun, to build the massive concrete gun emplacements for the five 10-inch guns of Fort Strong, one of the new Coast Artillery forts planned to defend Boston Harbor.