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 Historic District
The village of Blue Hill is located on the east coast of the Blue Hill Peninsula, at the head of Blue Hill Harbor, where two streams empty into the bay. Main Street runs roughly east–west, forming the spine of the village, with Union Street, Pleasant Street, Parker Point Road, and Ellsworth Street radiating away. The district includings properties on Main Street from west of High Street as far east as Ellsworth Street, along Union Street northwest to the area of the 1794 cemetery, and along Bucksport Road to High Street. There are more than 70 historically significant buildings in an area covering .
Although the village was settled in 1762, its oldest surviving element is the 1794 cemetery. The oldest buildings, dating to c. 1800, including the Daniel Spofford House and the Congregational Church Parsonage, the latter associated with the 1834 Greek Revival Congregational Church. The American Legion Hall was built in 1833 as the home to the Blue Hill Academy, which was founded in 1803 as the first school in Hancock County. The academy was later succeeded by the extant George Stevens Academy, whose main building, an 1898 Colonial Revival structure, stands in the district. George Stevens' 1814 Federal style house also still stands on Union Street.