Great Blue Hole
The Great Blue Hole is a giant marine sinkhole off the coast of Belize. It lies near the center of Lighthouse Reef, a small atoll from the mainland and Belize City. The hole is circular in shape, across and deep. It was formed during several episodes of quaternary glaciation when sea levels were much lower. Analysis of stalactites found in the Great Blue Hole shows that formation took place 153,000; 66,000; 60,000; and 15,000 years ago. As the ocean began to rise again, the cave was flooded. The Great Blue Hole is a part of the larger Belize Barrier Reef Reserve System, a World Heritage Site of the United Nations Educational, Scientific and Cultural Organization (UNESCO).
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.