Just 50 km from Valencia lies the longest cave in Europe that can be explored by boat.
We went there one weekend as a family outing. The cave tour starts with a boat ride through part of the cave, then about 200–300 meters on foot, and then back on the water again, leading to a small light show.
At times, the boat had to pass under very low ceilings.
Can’t see the water? It’s there.
The water in these caves is so still and clear that it feels as if the boat is floating in mid-air, partly thanks to the well-designed lighting.
With proper lighting, you can really see how transparent the water is.
Like in any old cave (around 2 million years old), there are plenty of stalactites and stalagmites, in which people tend to see “smiling jellyfish” and other imaginary creatures.
Radon in the cave — why are the guides wearing masks?
One unusual thing we noticed was that all the guides were wearing masks. It turned out this had nothing to do with dust or humidity.
The San José Cave is a limestone cave, but its rock layers contain uranium-bearing minerals that release radon — a radioactive gas.
For visitors who stay only briefly, the radiation levels here are considered safe. However, guides spend many hours inside the cave every day, so according to occupational safety regulations, they wear protective masks or respirators to reduce their cumulative exposure.
Practical information
The tour lasts about 45 minutes. It’s best to buy tickets online to avoid queues. Tickets cost around 15 euros as of 2025.
The temperature inside the cave is stable — around 20–21°C year-round. However, it feels closer to 18°C, so it’s a good idea to bring a light jacket.
