Per FGS Bulletin 66:
Lat/Long: 30 28 49.56870 83 14 39.70763
This spring issues from the bottom of conical depression. The spring pool diameter is about 72 ft (21.9 m) north to south and 82 ft (25 m) northeast to southwest. Pool depth measures 24 ft (7.3 m). The spring has vertical limestone walls. The 100 ft (30.5 m) long and 15 to 25 feet wide (4.6 – 7.6 m) spring run flows swiftly into the tannic Withlacoochee River. There was no visible boil in October 2001. Nearly the entire spring bottom and sides are covered with dark green algae. Sandy high ground surrounds the spring and rises to approximately 20 ft (6.1 m) above water level. Mixed hardwoods and pines occur along with numerous dirt pathways. An underwater cave system has been mapped at Madison Blue Spring.
High flow. Cobalt blue water. A lot of little circuits, the most famous being the Godzilla room circuit. You can go on the main line until it ends at a drop off room, but before that you can take the Mount offshoot to Potters delight, then Rocky Horror, then the Courtyard which has an amazing personality all its own.