The Fuente de los Baños emerges from the base of a limestone cliff at a constant 25°C year-round, a thermal phenomenon fed by aquifers heated deep beneath the Castellón interior. Montanejos owes its existence to these springs; Roman engineers built the first bathhouses here in the 2nd century, and medieval pilgrims traveled inland from Valencia specifically for the waters' reputed healing properties. The modern thermal pools were formalized in the 1980s, channeling the spring flow into accessible stone basins along the Mijares River, but the source itself has never varied in temperature or mineral composition since measurement began in 1891. Today the site draws visitors seeking a compact thermal experience without the infrastructure of coastal spa resorts. The main pool sits open to the sky, framed by poplar and willow, with a secondary basin carved into the cliff face where the spring emerges. Water chemistry reports published by the Castellón provincial government in 2025 confirm elevated magnesium and calcium sulfate levels, the same mineral profile that attracted the Romans. The site operates under a capacity system during summer months to preserve water quality and riverside vegetation; entrance is controlled between June and September, with a nominal conservation fee introduced in 2024. Montanejos itself remains a working agricultural village of fewer than 500 permanent residents, its economy historically tied to almond and olive cultivation rather than tourism. The thermal springs occupy a protected corridor managed by the municipal council, bordered upstream by the Chorro waterfall and downstream by a network of irrigation channels dating to Moorish rule. Most visitors arrive as part of organized half-day excursions from Valencia, a 90-kilometer route that climbs through citrus groves and pine forest into the Sierra de Espadán foothills. The journey takes roughly 90 minutes, positioning Montanejos as the closest true thermal spring system to the Valencian coast. Access to the springs is walk-in; no advance reservation secures pool entry, though capacity limits mean arrival before noon is standard guidance during high season. The site maintains basic facilities—changing rooms, footbaths, shaded rest areas—but no spa services or mechanized features. This is thermal bathing in its oldest form: mineral water, river stone, open air.