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.
Oxley Wild Rivers National Park
The Gara Gorge is located south-east of Armidale along the Castledoyle Road off the Waterfall Way just east of Armidale. The remains of Australia's first public hydro-electric scheme can be viewed here. Gara Gorge is picnic area with tables, drinking water, toilets and gas barbecues. Known for scenic bush strolls and the Blue Hole which is commonly used for swimming. The Threlfall Walk follows the route of the historic 1894 hydro-electric scheme, along old embankments and through ancient cuttings, to a lookout platform high above the river. Crombies Cave, the longest granite cave in Australia at , can be found in the next small creek, Powers Creek, an easy walk to the south of the Blue Hole. As the creek flows under the fence from the surrounding grazing country, within it begins its journey underground to come out down stream. The cave can be accessed from here and negotiated for at least half its length. It contains very beautiful granite sculptures, gnammas and potholes, some big caverns and a small sandy beach near the lower exit. A climb down a small waterfall and a curving squeeze can be difficult for some to negotiate. The exits downstream can be difficult to find from the outside.