The longest underground river in Europe is in Spain

• In the surroundings of the Sant Josep caves there are remains of human occupation from the Upper Paleolithic 17,000 years ago.

In Vall d’Uixó, in Castellón (Spain), there is a system of natural caves that developed during the Middle Triassic period, about 245 million years ago. This spectacular enclave has been the settlement of the inhabitants who populated this valley for centuries, so there is no specific date of its discovery.

We are talking about the Coves de Sant Josep or the San José grottoes, which consist of 2,750 meters of length, which includes the longest navigable underground river in Europe and which also maintains an unsolved mystery: no one knows where the river originates or where. This is the end of its route, which is lost inside the caves that are impossible to cross.

An 800-meter boat ride

Inside the cavity, the visit to the navigable underground passage begins at the pier. The total length of the underground river is 800 meters and later there is a pleasant 250-meter walk through dry terrain. The visit to the Coves de Sant Josep lasts approximately 45 minutes and the entire interior of the cave remains constant at 20 degrees of temperature throughout the year.

Declared a Site of Cultural Interest and World Heritage by UNESCO, the interior of the Coves de Sant Josep is made up of the Hall of the Bats, the Boca del Forn, Lake Diana, the Blue Lake, the Gallery of the Siphons, the Waterfall of the flower, the Rock, the Devil’s Lake, the Pachón Dog, in addition to being able to see stalactites and stalagmites along the dry gallery.

The Vall d’Uixó City Council offers several options to get to know this unique place in Europe, in addition to the aforementioned boat route, it can be done with kayaks or even through the ‘Singin in the cave’ program, a cycle of acoustic concerts inside the cave that is celebrated annually.

The Coves of Sant Josep through history

The first documented technical exploration of the interior of the grotto was carried out in 1897 with the aim of improving the use of the underground river for municipal use. However, despite not being enabled for tourist activity as at present, the area around the access to the caves has been a traditional meeting place for the local population to have picnics or to spend the day with friends and family.

Already in the 20th century, in order to avoid accidents for those who dared to enter the dark caves, a fence was placed for safety. The installation of electric lighting inside had to wait until the middle of the 20th century, initially planned for research purposes, but which began to attract the interest of tourists.

Finally, in 1958, the first topographical map of the cave would arrive, which, together with the population’s access to private vehicles and the carrying out of works to enlarge spaces and facilitate access, catapulted tourism to the area and reached 3,000 visits in 1960 and 20,000 in 1961.

Currently, incursions continue to be made inside the Coves de Sant Josep to explore and survey the unknown bowels of the cavity. Like the Sala d’en Guillem, the last gallery discovered in January 2023 and which reminds us that in this underground karst space there is still much to discover, and Mother Nature is continually giving us surprises and showing us its inexhaustible beauty.