The caves of El Águila are a gem of the geological heritage of Ramacastañas, in the province of Ávila. They cover a route of 1,000 meters that is accessible in almost its entirety, being in excellent state of conservation. With a depth of 50 meters, during the visit you will discover very singular formations of stalactites and stalagmites which reach a multitude of colours, shapes and sizes.
This is an interesting route in which the limestone formations stand out for their colours thanks to the lighting of the caves. With humidity that practically reaches all, the caves maintain a stable temperature of around 17ºC throughout the year. Although it is difficult to determine an exact date as far as their origin is concerned, experts believe that the current aspect of this very complex geological process as far as limestone formations are concerned could be dated to 12 million years ago. One of the most spectacular areas of the cave is the central vault, which covers almost 10,000 m2 and is full of surprising formations.
How did El Águila Caves originate?
El Águila Cave formation is made up of Paleozoic limestones that are attributed to the Lower Cambrian, i.e. they originated 500 to 540 million years ago. The rocks found in this cave are soluble under environmental conditions and if they are in contact with water, cavities can be created through a slow geological process.
Thus, the circulation of underground water from the Arenas and Avellaneda rivers originated a series of cavities related to the impermeable level of the subsoil. The widening of these cavities triggered a series of collapses of igneous rock that would form the great rooms that give rise to El Águila Caves. Last major collapses occurred more than 75,000 years ago.
As has happened with many other discoveries throughout history, especially in terms of caves, as was the case with the Nerja cave, the discovery of El Águila caves was a product of chance. As if it were a Christmas present, on December 24, 1963, five young people who were walking around the Romperropas hill, also called El Águila hill, were surprised to see steam coming out of a hole. This water vapour was the result of the contrast between the temperature inside, at about 17ºC, and the cold outside.
Curious, they used lanterns and ropes to enter through a small tunnel that was barely 60 cm in diameter. After the descent, the children crawled between 50 and 60 metres until they reached the enormous main vault. However, the adventure cost them time, as they were lost for five hours inside the caves until they finally found the hole through which they had entered. Seven months later, after the work to fit out this space, the caves of El Águila opened to the public on 18 July 1964.
Incredible stalactite and stalagmite formations
Among all the surprises of this natural space, what is most striking is the variety of textures and colours that can be seen here. The formations are the product of a long evolution in which the process of transformation has been continuous, with repeated phases of creation and destruction, resulting in a wide diversity of the underground landscape.
Thus, the caves of El Águila have a wide variety of speleothems: stalactites, stalagmites, speleothems and columns, eccentric, anthodontic, shields, needles and even moon milk (a white substance found inside some caves, with the characteristic that it does not harden or turn into stone). To understand the grandiosity of the complex formed by El Águila caves, we must know that it is estimated that a speleothem grows about one centimetre every 150 years.
These speleothems, as explained above, are the result of the slow filtration of rainwater, while the currents of underground water are responsible for creating the cavity. Therefore, when the cave stopped functioning as an underground conduit, the water that filtered loaded with CO2 dissolved the calcium carbonate creating these marvellous formations. As for the variety of crystalline growth in the Águila caves, these are a consequence of the changes in the microclimate of the cave as well as the context in which the formations arise.
At some point unknown thousands of years ago, the ground gave way a few centimetres, which caused many columns to break, and these have a flat separation that can be seen between the two pieces at half height.
Another particularity of the caves is their climate, which is stable with a temperature that varies between 15ºC and 17ºC, with a relative humidity of 100%. However, environmental changes outside have affected the temperature of the cave, which has changed by 2ºC in the last 30 years.
The stalagmites found here have made it possible to understand the cause of the maximum extension of the Gredos glaciers, which took place 26,000 years ago, related to rainfall in the region during a very cold period of time. Moreover, thanks to their special characteristics, scientists have been using El Águila Caves for more than five years as a natural laboratory for the analysis of past and present climate change.
Visits to the caves and the Sierra de Gredos Park
The caves of El Águila are located on the hill of Romperropas, also called the hill of El Águila, giving the caves their name. This way, the limestone rock is hidden by the forest above the hill, so the underground landscape of the caves is even more striking. The route to the caves of El Águila is always made by a guide who informs about the discovery of the caves, their formation and the special characteristics of this karstic cavity. With about 1,000 meters of route, the walk between stalagmites and stalactites takes approximately 40 minutes.
As for the surroundings, the hill that shelters the caves is in the heart of the Tiétar valley, in full contact with nature. In turn, the valley is within the Sierra de Gredos Regional Park, a magnificent natural creation sculpted by glacial erosion. In the Sierra de Gredos there are many gorges and lakes, making it a place with excellent hiking routes.