The highlight of the park, Onondaga Cave is renowned as one of the most spectacular show caves in America because of the quality of its formations. The natural entrance to the cave is a spring, and was not discovered untill 1886. Several entrances were dug into the cave for access and to give tours, but all except for one have been sealed off. Ownership of the cave has exchanged hands several times, even causing court disputes, but eventually became a state park in 1981. It is now also a National Natural Landmark.
Guided tours are led throught the cave along a lighted, paved walkway. Tour guides give information about the geology of the cave, and help to showcase the many formations found in the cave. Those formations and features include many stalactites, stalagmites, flowstones, soda straws, draperies, and cave coral, and some are so unique, they have been named, such as King's Canopy, the Twins, and the Lily Pad Room. Tours usually last a little over an hour, and are just under a mile in length. Typically, tours are given from March thru October. The cave is 57ºF year-round, so be sure to dress appropriately.
At 15,639 feet long, Catherdral Cave is much longer than Onondaga Cave, but tours are only offered on the weekends. Tours are generally given between Memorial Day and Labor Day weekends, and is a lantern tour lasting around two hours. The tour is much more strenuous than Onondaga, and is limited to the first 30 people. The total length of the tour is about one and two-thirds mile round trip, and usually lasts around two hours. Tours begin near the campground showerhouse, and inlcude a one-third mile walk up Deer Run Trail. The cave tour itself is approx. 1 hour and 30 minutes, the rest of the time is spent to and from the entrance along the trail.
The commercial/tour section only covers a portion of the cave, mainly because of ease of acces, and to preserve cave life in other areas of the cave. Along the tour, visitors will see many formations such as flowstones, slump pits, a natural bridge, and a room with a nearly 80-foot ceiling. Also along the tour, just before the switchback, visitors will see the CCM, or Cathedral Cave, Missouri Seismic Station. This earthquake monitoring device was installed in 1989, and is operated by St Louis Iniversity. Data gathered by this monitor is sent via fiber optic cable to the visitor center, where it is processed and sent by satellite to the National Earthquake Center in Golden, Colorado.