Blue Hole (Castalia)
The Blue Hole captured the public’s interest because of its size, about in diameter, clarity, vibrant blue hue, and enigmatic "bottomless" appearance. Contrary to prevalent belief, the depth of the Blue Hole is not unknown, but has been sounded and found to be about deep. Water temperature is about throughout the year. Floods and droughts have no effect on temperature or water level. The Blue Hole is fed by a passing underground stream which discharges of water daily into Sandusky Bay to the north, feeding into Lake Erie. The water contains lime, soda, magnesia and iron, and because the Blue Hole is anoxic, it cannot naturally sustain fish. The surrounding terrain is developed on limestone bedrock and exhibits karst topography due to dissolution of the limestone by ground water, creating water-filled sinkholes. The Blue Hole was known to American Indians and was first recorded in history in 1761. Several similar blue holes are known to local residents. The Blue Hole that once was a tourist attraction is now off limits to the public. It is located on the grounds of Castalia Trout Club. It is to be distinguished from another hole similar in size and eerie bluish-green color. This latter hole is owned by the Castalia State Fish Hatchery operated by the Ohio Department of Natural Resources, Division of Wildlife and is open for public viewing.
Blue Hill (CDP), Maine
The Blue Hill CDP consists of the main village within the town of Blue Hill. The CDP is located at the geographic center of the town, surrounding the head of Blue Hill Harbor, an arm of Blue Hill Bay. The CDP extends south along Route 175 as far as Bragdon Brook, just north of Blue Hill Falls; southwest along Routes 15 and 176 as far as Grindleville Road; west along Route 177 (Union Street) to Field House Lane; northwest along Route 15 past Mountain Road to the southern slopes of Blue Hill; northeast along Route 172 past Mountain Road; and east along Route 176 to Peters Cove and Little Peters Brook. The summit of Blue Hill is just outside the CDP to the north.