What is the name of the famous cave system in Custer, South Dakota, and how deep is it?

The famous cave system in Custer, South Dakota is called the Jewel Cave National Monument. It is one of the longest caves in the world, with over 200 miles of mapped and surveyed passages. The cave system is located in the Black Hills, near the town of Custer, and is part of the National Park Service.

The Jewel Cave National Monument has several chambers and unique formations, such as stalactites, stalagmites, and flowstones. The cave also has rare and delicate formations, such as boxwork, which is found only in a few caves in the world.

The deepest part of the Jewel Cave National Monument is over 700 feet deep, making it one of the deepest caves in the United States. The cave system is still being explored and mapped, and there may be even more passages and chambers yet to be discovered.

If you're interested in visiting the Jewel Cave National Monument, guided tours are available throughout the year. The tours range in difficulty and length, from easy and short to strenuous and long. Visitors are encouraged to wear appropriate clothing and shoes, and to bring a light jacket, as the temperature inside the cave is a constant 49°F (9.4°C).

The famous cave system in Custer, South Dakota is called Jewel Cave National Monument. It is the third-longest cave system in the world, with over 215 miles of mapped and surveyed passages. The deepest point in the cave is 823 feet below the surface.

Jewel Cave is known for its beautiful calcite crystals, which are often referred to as "jewels". The cave is also home to a variety of other cave formations, including stalactites, stalagmites, and flowstone.

Jewel Cave National Monument is open to the public for tours. There are a variety of tours available, ranging from easy to strenuous. Visitors can learn about the cave's geology, history, and wildlife on these tours.