Blue John Cavern is a famous limestone cave located in the Peak District of England, near the village of Castleton. It is renowned for its stunning mineral formations, particularly the unique blue and yellow banded mineral known as Blue John, which is found only in this area. The cavern attracts many visitors who come to explore its impressive stalactites and stalagmites. The cave has a rich history, having been mined for Blue John since the 18th century. Today, guided tours allow visitors to learn about the cave's geology and history while enjoying its natural beauty. The cavern is an important part of the local heritage and contributes to the area's tourism.