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).
Blackheath, New South Wales
Blackheath (postcode: 2785) is an Australian town located near the highest point of the Blue Mountains, between Katoomba and Mount Victoria in New South Wales. The town's altitude is about and it is located about west north-west of the Sydney central business district, north-west of Katoomba, and about south-east of Lithgow.