The cave of the Bells is a fascinating and fragile underground wilderness which exerts its strongest appeal on Forest visitors who enjoy cave exploration. Though this subterranean gallery of rock, known for its unique and varied suite of minerals and formations, has been thousands of years in forming, it is nevertheless extremely fragile. A few moments of thoughtlessness here could cause immense amounts of damage. For that reason, and because so many similar areas have been damaged by vandalism, the Cave of the Bells is locked and gated. For a small deposit, keys are available at Forest offices in Nogales and Tucson to those who wish to visit this unique area.
The Cave of the Bells is located in Sawmill Canyon at the end of a four-wheel-drive road on the eastern slopes of the Santa Rita Mountains. Lake Tunnel, one of its most notable and accessible passages, leads through a large room to a permanent lake far underground. The lake is a total of 80 meters below the entrance level. Visitors to this area note an unusual temperature gradient. Instead of getting cooler as the cave gets deeper, the temperature becomes noticeably warmer. The lake itself has been measured at 76 degrees Fahrenheit, nine degrees warmer than the air at the entrance. For this reason, it is believed that the water in the lake is heated by sources far below.
Nearby Onyx Cave is open by permit also and should be treated with the same respect.