High Quality Content by WIKIPEDIA articles! Dark Island, a prominent feature of the St. Lawrence Seaway, is located in the lower (eastern) Thousand Islands region, near Chippewa Bay. A historic landmark here, "The Towers" was long known as Dark Island Castle until recently renamed "Singer Castle". The island itself sits only a few yards south of the Canadian-United States border that runs along the river. Because of its proximity to Canada, it was used for rum-running during prohibition in the United States.