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 near Cave City, Kentucky, is the world's longest cave. More than 367 miles (591 km) of passages have been mapped. To get an idea of how long Mammoth Cave is, you should consider that the second longest cave in the world, Optimisticeskay Cave, in the Ukrainskaya region of the C.I.S. (former Soviet Union), is only 143 miles (230 km) long. Mammoth Cave is three times longer than its nearest competitor. Not only is the cave the longest in the world, but cave mappers believe the cave system will eventually prove to be 560 miles (900 km) long! Mammoth Cave was formed in Mississippian-age limestone rock. The cave is 379 feet (118 m) deep, and contains at least 5 levels of passages.