The spring originates from a siphonic karst system, meaning it is fed by a complex, largely unexplored network of submerged limestone caverns.
The phenomenon known as 'intermittency' occurs when the water discharge suddenly increases during high precipitation, causing the spring to 'roar' as the internal conduits reach capacity.
The water temperature remains relatively constant year-round, typically hovering around 10 to 12 degrees Celsius.
La Fuentona is officially classified by the Government of Cantabria as a 'Monumento Natural' due to its unique hydrogeological importance.
The spring forms the headwaters of the River Verde, which runs for approximately three kilometers before joining the Saja River.
La Fuentona de Ruente is a natural spring located in the Saja-Besaya Natural Park, distinguished by its karst origin where water emerges from a siphon at the base of a limestone cliff. The site is a Hydrological Monument of Cantabria, characterized by the irregular periodicity of its water flow. During heavy rain, the flow rate increases dramatically as the underground reservoir fills and creates a pressure-driven surge. The spring feeds into the River Verde, a tributary of the Saja River, within the municipality of Ruente. It is surrounded by a dense riparian forest of oak, hazel, and ash trees. The geological composition consists of a complex system of underground galleries in the Cretaceous limestone massif.
The wooden footbridge overlooking the blue-green water of the main spring pool.
Wear waterproof footwear as the area surrounding the spring pool can be muddy or slick even in dry weather.
Bring a raincoat or umbrella if visiting after heavy rainfall, as the increased flow can cause the area to mist or splash.
Combine the visit with a walk through the town of Ruente to see its traditional 'casonas montañesas'.
Do not attempt to enter or climb the limestone cave opening, as it is a protected geological site and dangerous due to sudden water surges.
Stay on marked gravel paths to protect the fragile riparian vegetation; swimming in the spring pool is prohibited.
