Sinkholes—which make the Earth look almost as though it's being swallowed from within–look like vertical caves. They are home to a variety of exciting discoveries, including floating islands, stalactites, rare plants, and endangered animals. From the mountains of China to the warm waters of the Caribbean, these amazing natural wonders pockmark the surface of our planet. They are mysterious and beautiful, and attract scientists, tourists, jumpers and divers, and others. Here are 10 best examples.