The Fuente de los Baños emerges from limestone bedrock at a constant 25 degrees Celsius, fed by subterranean channels that have carved the Mijares River valley for millennia. Roman engineers built the first bathing infrastructure here in the second century, recognizing the strategic value of a geothermal spring that never freezes. Today's pools retain that utilitarian geometry—rectangular concrete basins set into the rock face, their turquoise water visible from the access road that winds through the Alto Mijares Natural Park. The site sits at the confluence of two hydrological systems. The thermal spring itself rises from Jurassic aquifers 800 meters below ground, heated by geothermal gradients and rich in calcium sulfate. Ten minutes upstream, the Chorro waterfall drops 15 meters over travertine ledges, its flow dependent on seasonal rainfall and snowmelt from the Sierra de Espadán. Visitors to Valencia Montanejos thermal springs & waterfall navigate both ecosystems in a single morning—the warm mineral pools for bathing, the cold river cascade for photography and canyon walks. Montanejos remained isolated until the 1970s, when paved roads connected the village to Castellón de la Plana, 65 kilometers east. The provincial government formalized public access to the thermal pools in 1982, installing changing facilities and imposing a seasonal entrance fee during July and August to manage capacity. The Chorro trail opened in 1995, a one-kilometer route maintained by the local council. By 2010, Montanejos thermal springs tours had become standard weekend itineraries from Valencia, with operators adding optional rafting on the Mijares or rappelling in the Montán Gorge. Archaeological surveys in 2003 uncovered Moorish cisterns beneath the current bathhouse, evidence that medieval settlers also harnessed the spring. The water's mineral composition—low in sulfur, high in bicarbonates—distinguishes it from volcanic hot springs found elsewhere in Spain. Its therapeutic reputation rests on consistent temperature rather than exotic chemistry. Conservation protocols introduced in 2018 limit daily visitor numbers during peak season, a response to algae blooms caused by sunscreen runoff. The pools remain accessible year-round, their appeal shifting with the seasons—summer crowds versus winter solitude, the surrounding beech forest turning copper in November.