Geologists trace the thermal source to rainfall absorbed in the Sistema Ibérico massif, where water descends through fractured Cretaceous rock, warming gradually over decades before resurfacing in Montanejos. The spring's output—roughly 300 litres per second—has carved travertine terraces along the Río Mijares, depositing calcium carbonate in fern-like patterns that harden into pale gold platforms.
Medieval records cite the pools as a cure for rheumatism, and by the 19th century, Castellón's gentry built balnearios along the riverbank. Today the site balances conservation with access: a €3 fee funds trail maintenance and seasonal lifeguard posts, while capacity limits during July and August protect the riparian corridor. The main pool, Poza de la Fuente, sits beneath a 15-metre cascade where spring water mixes with the cooler river current. Upstream, the Chorro del Salto drops 60 metres through a moss-lined gorge, accessible via a 1.2-kilometre footpath that climbs 80 vertical metres.
The Montanejos thermal pools and waterfall tour attracts hikers and thermal-water enthusiasts in equal measure. Winter mornings see steam rising from the pool surface as air temperatures drop to 5°C, while summer afternoons fill the shallow basin with families wading through knee-deep water. The trail to Chorro del Salto passes through Aleppo pine stands and wild rosemary thickets, with viewpoints over the Mijares canyon every 200 metres. Biodiversity surveys count 42 bird species along the corridor, including grey wagtails and Bonelli's eagles nesting in the gorge walls.
The site's geology remains its defining feature. Travertine formation continues at roughly 2 millimetres per year, building new ledges where algae and moss colonize within weeks. The spring's mineral content—magnesium, calcium bicarbonate, and trace sulphur—gives the water a faint alkaline taste and a turquoise tint in direct sunlight. Guided walks explain the hydrological cycle and point out fossilized gastropod shells embedded in older travertine layers, evidence of the spring's activity over millennia.
8 hr 30 min
