Blue Hole (Castalia)
The Blue Hole is a fresh water pond located in Castalia, Erie County, Ohio, in the United States. From the 1920s to 1990 the Blue Hole was a tourist site, attracting 165,000 visitors annually at the height of its popularity, partly because of its location on State Route 269, about southwest of the Cedar Point amusement park in Sandusky, Ohio.
Blue Mountains (New South Wales)
Following European settlement of the Sydney area, the area was named the "Carmarthen and Lansdowne Hills" by Arthur Phillip in 1788. The Carmarthen Hills were in the north of the region and the Lansdowne Hills were in the south. The name "Blue Mountains", however, was preferred and is derived from the blue tinge the range takes on when viewed from a distance. The tinge is believed to be caused by Mie scattering which occurs when incoming light with shorter wavelengths is preferentially scattered by particles within the atmosphere imparting a blue-greyish colour to any distant objects, including mountains and clouds. Volatile terpenoids emitted in large quantities by the abundant eucalyptus trees in the Blue Mountains may cause Mie scattering and thus the blue haze for which the mountains were named.