Inside Warm Mineral Springs Florida is dotted with cenotes, hourglass-shaped sinkholes caused by underground water eroding the rock until a portion caves in. What sets the Warm Mineral Spring apart is its deep aquifer source, instead of groundwater. Depth Stalactites prove that the cavern roof was once above water. Remains of ancient animals and prehistoric man show use of the spring at least 10,000 years ago, when sea levels were lower. Most artifacts have been found on a shelf about 40 feet down. The warm spring source pours out mineral-laden, low-oxygen water from a deep aquifer, at a temperature of 97 degrees. A smaller inlet emits cooler water, blending to keep the spring at a temperature of 83 to 85, at a rate of 8 million gallons per day. Mouth of spring 20? Shelf 40? 60? 80? Lower cavern 100? 120? Rock detritis 140? The bathing area encircling the spring is marked with a ring of floats to warn bathers of a steep drop-off. The spring offers the most highly mineralized water of any in the country. Ponce de Leon, seeking the fabled Fountain of Youth, landed in Charlotte Harbor on his final voyage in 1521. This gave rise to the spring's claim as the true Fountain. 160? 180? Source SOURCES: Sarasota County; warmmineralsprings.com linked documents 200? The floor of the spring has a mound of rock detritus from the collapse of the ancient cavern roof, topped by a layer of silt. STAFF GRAPHIC / BARRY McCARTHY