The "Great Pagosah Spring" holds the title World's Deepest Geothermal Hot Spring. On August 20, 2011, this "Mother Spring" was measured to an astounding 1,002 feet deep. But no one really knows just how deep it is. No plumb line has ever reached the bottom! While it is much too hot for a soak, this natural hot spring feeds geothermic mineral water to all of Pagosa Springs' hot spring pools.