A valley of warm water in the middle of the mountains
Montanejos is a village of just over 600 people in the Alto Mijares, wedged between limestone walls and surrounded by pine trees. What makes it special is a few metres downstream: a thermal spring that flows at 25 ºC every month of the year and has drawn people to the Mijares canyon for centuries.
The spot is called Fuente de los Baños. It's not exactly a fountain: it's a stretch of river fitted with walkways, natural pools and turquoise water that stays the same temperature regardless of the season. People wade in during January while it's cold in the village. In August there are queues at the gate.
Spain's first thermal zone to earn the Blue Flag. The water emerges from the ground at 25 ºC every day of the year, rain or snow on the sierra above.
Fuente de los Baños
The water rises in a small cave behind a masonry wall decorated with ceramic tiles, flows into the riverbed and forms a continuous turquoise sheet. The seven-spout fountain that channels it carries a legend: it is said to have been built by King Abú Zayd, the last Almohad ruler of Valencia, for his court's baths. The remains of those 12th-century Arab baths are still preserved on the right bank of the river.
The history of the place goes deep. The waters were declared of public utility in 1863. By the 18th century, the sick were already travelling here to take the thermal waters. Between the 18th and 19th centuries, health tourism turned Montanejos into a provincial landmark, and in 1997 the modern Balneario (spa) opened in the village, combining therapeutic treatments with access to the river area.
The area runs between the Puente Nuevo bridge and the spring. In summer, entry is paid with controlled capacity and advance booking required on the official website. The rest of the year, entry is free with no reservation needed. Guests staying overnight in the municipality get a discount on admission.
It's worth knowing the rules before you arrive:
- No pets
- No cool boxes or large amounts of food (one sandwich and one litre of drink per person permitted)
- No inflatable floats, airbeds or boards
- No camping equipment (one chair per person permitted)
What to see and do
The valley offers far more than a dip. The Montanejos area concentrates some of the most interesting routes and landscapes in inland Castellón.
Los Estrechos is the most dramatic stretch of river: a 9 km gorge with walls up to 100 metres high and barely 25 metres wide. It is also one of the most popular climbing areas in the province.
The Ruta de las Fuentes covers 15 km and links the main springs in the area, passing mills, irrigation channels, washing stones and orchards along the river, starting from the village itself. The Sendero de los Estrechos (9 km) runs alongside the river through the interior of the gorge.
Further up, Embalse de Arenoso has calm water suitable for kayaking or stand-up paddleboarding, plus walking paths along the bank. Next to the dam, the Chorro de Arenoso releases up to 41 m³ of water per second when operating: noise, foam and a spectacle worth the detour even if you're not planning a swim.
In high season several companies in the village offer rafting, canyoning, via ferratas, kayaking, caving and bungee jumping. Montanejos works well as a base for a few days of active mountain exploration in the Alto Mijares.
How to visit Montanejos from Onda
From Onda, take the CV-20 towards the Mijares and follow the valley upriver to Montanejos. It's 39 km and about 45 minutes of driving, with scenery that improves as you gain altitude. There is no useful public transport: a car is essential.
The typical plan is a full day: swim in the morning (when the canyon is still in shade and the water is calmer), lunch in the village and a hike or walk in the afternoon. If you're going in summer or on a fine weekend, book your ticket online in advance and arrive early to find parking. At other times of year the area is noticeably quieter and the experience is completely different.
Where to eat in Montanejos
The village has several bars and restaurants around the square and along the access road, with set lunch menus aimed at day-trippers. In high season it's worth booking ahead or timing your lunch to avoid the post-swim noon rush. If you prefer more choice, Onda is 39 km away.