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.
Happy Valley, Hong Kong
On 19 December 1941, the Japanese Imperial Army entered the hill east of the valley and fought their way to Blue Pool Road. On (now Blue Pool Road) a number of large massacres occurred, most notably the Blue Pool Road Massacre, where civilians were bayoneted. Civilians and Soldiers captured were kept in the appalling conditions of 'the black hole of Hong Kong' (a house on Blue Pool Road). The Japanese later advanced up to Wong Nai Chung Gap, where the battle of Wong Nai Chung gap occurred, resulting in Japanese control of the gap. Although the low-areas of Happy Valley were captured, areas surrounding Leighton hill and Morrison Hill were still contested until later in the Battle of Hong Kong.