Colossal Cavern, near Mammoth Cave in Kentucky, is part of a connected cave region that includes Bedquilt Cave and lies deep beneath Chester Sandstone in Saint Louis Limestone. Its steady cool temperature, notable formations, and vast chambers were formed by water rather than earthquakes or eruptions once imagined. After the Louisville and Nashville Railway acquired the property in 1896, a new entrance was made and the cave was carefully surveyed. It later gained major speleological importance through links to Salts Cave, other passages, and finally Mammoth Cave, helping create the Flint-Mammoth Cave System. Its Bedquilt section also inspired the pioneering text adventure game Colossal Cave, later known as Adventure.