Cathedral Caverns State Park is located near the town of Grant, in northeastern Marshall County. Although the cave has been open as a commercial operation at various times since 1955, it was not until May 2000 that it became officially opened to the public as Cathedral Caverns State Park. Operations of the park are overseen by the Alabama Department of Conservation and Natural Resources. Ranger-guided tours are provided throughout the day and take approximately one hour. In addition to the cave tour, the park has a welcome center, picnic areas, and primitive tent camping. In 1995, Cathedral Caverns provided the cave setting for the Disney Studios film Tom and Huck. In 2009, the park had 39,000 visitors, annual operating expenses of $351,000, and a staff of six people.
The caverns are located in the Cumberland Plateau physiographic section of Alabama and formed within Mississippian Period limestone deposited between 350 and 320 million years ago. Archaeological excavations at the cavern's mouth indicate that human use of the cave by Native Americans dates back to 8,000 years ago. In modern times, the cave was originally called Bats Cave and was operated as a private attraction by local entrepreneur Jay Gurley from 1955 to 1974. It was Gurley who adopted the Cathedral Caverns name, reportedly after his wife commented that the cave's soaring ceiling, with its dramatic stalactites and stalagmites, looked "like a cathedral." In 1972, it was declared a National Natural Landmark. Two years later, the Gurleys ran into financial problems, and the cave was sold at auction and remained in private hands until the state of Alabama bought the cave and 461 acres of surrounding land in 1987. Funding delays postponed the state's plans to open the cave as a state park until 2000, however.
The public areas of Cathedral Caverns traverse approximately two miles of trails, but there are many more passages that are not open to the public. Some 11,000 feet of passages have been mapped, but the total extent of the cave system is unknown. Access to Cathedral Caverns is provided by a paved and lighted pathway. Its massive entrance is 128 feet across and 25 feet high, making it the largest commercial cave opening in the world. The trek from the mouth of the cave to its farthest reaches is a little more than a mile along the sloping and twisting walkway. It is also wheelchair accessible. The cave is a constant 60 degrees year round. The largest chamber, known as the Big Room, is 792 feet long and 200 feet wide. Other cave formations include the world's largest stalagmite, Goliath, which is 45 feet tall and 243 feet around, another stalagmite that is 35 feet tall and only three inches around, a stalactite forest, and a 135-foot-long wall of flowstone that resembles a frozen waterfall.
Mystery River flows through the cave, and some of the passages are subject to flooding during periods of high rainfall. About 2,700 feet of passage are not open to the public, including the Crystal Room, which is full of delicate formations composed of fragile pure white calcite. These formations would be degraded by the heat, humidity, and movement of visitors.