Where is the longest navigable underground river in Europe? Is it possible to sail on it?

The province of Castellón has a beautiful natural secret in store for us just a few kilometres from the Mediterranean beaches: an underground river that is almost three kilometres long. And you can even sail across it!

Cuevas de Sant Josep, Castellón
The Caves of Sant Josep contain a navigable river of almost three kilometres, although its total length is still unknown. Image: covesdesantjosep.es

In the heart of the province of Castellón, in the charming town of La Vall d’Uixó, and just 15 minutes from the Mediterranean Sea, there are caves whose beginning and end are a mystery. However, what is known for certain is that the Caves of San José, known in Valencian as Coves de Sant Josep, are accessible to the public.

They have a length of 2,750 metres, and are home to the longest navigable underground river in Europe. For millennia, the flow of water has sculpted this spectacular underground landscape, allowing us to explore it today on foot, by boat or kayak. With a constant temperature of 20 ºC, these caves are ideal to visit at any time of the year.

How to visit the Caves of Sant Josep

Visitors to the Coves de Sant Josep will enjoy a relaxing boat ride along one of the most impressive navigable underground rivers. The visit includes an 800-metre boat ride and a 250-metre walk, taking approximately 45 minutes in total. The cave is illuminated with LED lights, which not only enhance the visual experience, but also help preserve the environment and prevent the proliferation of moss.

During the tour, visitors can admire the incredible heritage of the caves, including a series of prehistoric paintings and engravings recognised as World Heritage by UNESCO. At the beginning of the cave, above the riverbed, there is a painting of a horse's head, and near it, on a panel, there is a meander painted in red on the wall.

On special dates, such as Halloween or Christmas, concert cycles and other special activities are held.

The cave paintings in the Sant Josep Caves date back to the Magdalenian period, and the first were discovered in 1993. Continued excavations have revealed that the cave was already inhabited in the Upper Paleolithic, approximately 16,000 years ago.

Useful information about the Caves of Sant Josep

Below, we offer you some interesting information in case you plan to visit this surprising place soon.

  • Location: Paratge de Sant Josep s/n, in La Vall d´Uixó (Castellón), just 15 minutes from the Mediterranean coast.
  • Email: [email protected]
  • Telephone: +34 964 69 05 76
Cuevas de Sant Josep, en Castellón
The underground river of the Caves of Sant Josep can also be explored by kayak. Image: covesdesantjosep.es
  • Opening hours: Monday to Sunday, 09:45 to 15:30. Please arrive 10 to 15 minutes before your visit time. The boarding staff will provide all the necessary instructions to ensure safe boarding and disembarking.
  • Other activities at the Sant Josep Caves: caving and kayaking and musical performances with the Singin’ in The Cave experience.
The Coves de Sant Josep were developed in the Middle Triassic period and are composed mainly of limestone. The origin of the river and the end of the cave are unknown.