Braidwood is a city in Will County, Illinois, United States, approximately 53 miles (85 km) southwest of Chicago and 18 miles (29 km) south of Joliet. The population was 5,203 at the 2000 census. The Braidwood Nuclear Generating Station, a nuclear power plant currently owned by Exelon Corporation, is also located in the area (although the plant's address is actually in the nearby town of Braceville).
The Son Doong Cave in Vietnam is the biggest cave in the world. It's over 5.5 miles long, has a jungle and river, and could fit a 40-story skyscraper within its walls. But nobody knew any of that until about six years ago.
Mammoth Cave, in Kentucky, a horizontal cave, is the longest cave system in the world, stretching for at least 390 miles (627 kilometers) beneath the surface of the Earth. However, some caves turn this tidy formula on its head and form from the bottom up. Water trapped in aquifers deep inside the Earth sometimes comes into contact with sulfide-loaded rocks, like pyrite, Orndorff said. This creates sulfuric acid, which, with enough hydraulic pressure, can push up through the rock to carve out a cave.