Cave of Sant Josep, the longest navigable underground river in Europe

Les Coves de Sant Josep in the municipality of La Vall de Uxó (Castellón), are located on the Costa de Azahar, near the Sierra de Espadán Natural Park. Inside the Sant Josep cave is the longest navigable subterranean river in Europe, a real spectacle for those who enter its waters. A journey to the interior of the Earth in which to admire this cultural and geological heritage.

Photo: Comunicación - Cueva de Sant Josep
Photo: Comunicación - Cueva de Sant Josep

The cavity has an active upwelling arising in limestone during the Middle Triassic period. However, what is curious is that despite the many visits made by different speleologists to the cave, the origin of the river and the end of the cave is still not known. Also interesting is the temperature inside the Sant Josep cave, which remains constant at 20ºC throughout the year. It is currently 2,750 metres long, making it the longest cave in Castellón and the second longest in the Valencian Community.

History of the Cave of Sant Josep

Photo: courtesy of Sergio Laburu, Roberto F. García, www.espeleofoto.com and Coves de Sant Josep
Photo: courtesy of Sergio Laburu, Roberto F. García, www.espeleofoto.com and Coves de Sant Josep

The importance of this cave is such that before the advances of the 20th century, famous historians such as Sebastian Miñano, J. Cavanilles or Pascual Madoz had already mentioned the existence of the San José cave in their works on geography. Moreover, it was known that the cave was already known in the Upper Palaeolithic, that is, approximately 17,000 years ago. This was demonstrated by the archaeological sites found at the entrance to the cave next to the cave paintings, which have now been declared a UNESCO World Heritage Site and a Site of Cultural Interest. For this reason the entrance to the cave was moved.

Photo: covesdesantjosep.es
Photo: covesdesantjosep.es

The proximity of an Iberian settlement also indicated that during the Iberian period the cave was already known and explored. It is also known that the Romans knew of its existence, as can be seen from a tombstone dedicated to Caio Cneo Craso, who was the son of the Roman consul Marcus Licinius Crasus.

The first known exploration was not carried out until 1902, when the Boca del Forn was reached, a narrow pass that was left free by the waters at that time that marked the limit of the accessible part of the cave.

In the years that followed, interest grew in discovering every detail of the Sant Josep cave. Thus, in 1915, the historian Carlos Sarthou Carreres made a partial exploration. A year later, the locals went beyond the Boca del Forn and reached the Lago de Diana. However, they found the Galería de los Sifones to be an insurmountable obstacle.

Photo: courtesy of Sergio Laburu, Roberto F. García, www.espeleofoto.com and Coves de Sant Josep
Photo: courtesy of Sergio Laburu, Roberto F. García, www.espeleofoto.com and Coves de Sant Josep

Later on, the cave began to be fitted out to facilitate visits and to allow boats to pass through. Thus, in 1950, the Boca del Forn ceased to be the limit of the cave’s route.

In 1954 the first speleological exploration was carried out and four years later the first topographical plan of the cave of Sant Josep was drawn up. In 1960 it was confirmed that the cave continued to be visited when it passed the Galería de los Sifones. This pass was blown up with dynamite and the Blue Pond was discovered, as well as the other galleries that make up the current route. There is also the Galería Seca. In the following years, new galleries and siphons are discovered until the known end of the cavity, exceeding 2,000 metres in length.

Travelling through the longest navigable underground river in Europe

Photo: Comunicación - Cueva de Sant Josep
Photo: Comunicación - Cueva de Sant Josep

The entrance to the cave of Sant Josep has been fitted out as a jetty for tourist visits to the cave. From here a boatman guides the small boats through a journey that takes about 40 minutes and navigates for 800 metres, as the remaining 250 metres of the visit are for the dry gallery. This is a mysterious and, above all, silent space, where water has shaped the rocks at will over thousands of years, finding very curious shapes.

Photo: Comunicación - Cueva de Sant Josep
Photo: Comunicación - Cueva de Sant Josep

In this way, a route that ends in the Sala de los Murciélagos begins from the pier. It is the first of the great rooms. Its name refers to the large number of bats that used to inhabit the San José cave. Here the vault stands out, with thousands of shapes sculpted by water. Leaving this room and after passing by the lovers’ walk, Lake Diana appears, with its five meters of depth. It is characterised by the colours green because of the moss that grows in the dark areas, although it is artificially lit.

Shapes sculpted by water | Photo: covesdesantjosep.es
Shapes sculpted by water | Photo: covesdesantjosep.es

After this you reach the Boca del Forn, an old artificially enlarged siphon. Passing through this gallery you reach a new narrow pass, the Galería de los Sifones, an old flooded siphon 60 metres long. It is the longest artificial tunnel of the route. Here live some crustaceans that are only found in this type of natural spaces.

Afterwards, the Galería Seca appears, where on the rock, thanks to the play of lights and shadows, original formations stand out, such as the Cascada de la Flor, which, when it rains, adds to its curious design the fall of the water. At the end of this, the route joins up again with the flooded gallery.

Photo: Comunicación - Cueva de Sant Josep
Photo: Comunicación - Cueva de Sant Josep

In this way, when you walk the 250 meters through a corridor guided by the rocks, you reach another jetty. Before getting back on the boat, you can see the beginning of a dark tunnel that leads to the cave already explored but closed to the public. About 1950 metres in total, in which the secret of the beginning of the underground spring of the cave of Sant Josep is hidden. Few people have entered this part of the cave, speleologists and experts.

Before the end of the visit, and back in the boat, you can see the area known as The Cathedral, as it has a vault 12 meters high. Here you can see strange stalactites hanging all over the room, such as La Medusa, which is reminiscent of the jellyfish.

Concerts in the interior of the Earth

Kayak expeditions | Photo: Comunicación - Cueva de Sant Josep
Kayak expeditions | Photo: Comunicación - Cueva de Sant Josep

During the summer months short acoustic concerts are usually held in the Sala de los Murciélagos, as well as longer ones in the area of the pier. The capacity is limited to six boats. In order to enjoy this activity it is necessary to purchase tickets in advance. A whole musical show in a unique setting. Another of the activities carried out in the San José cave are the kayak expeditions with swimming included, although they are only carried out in the low season.


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