Portal de Turismo de Castilla y León

Welcome to the Ojo Guareña Natural Monument Visitors’ Centre

Just like the rest of the park visitors’ centres, all throughout the region of Castilla and León, this is the recommended access point for these nature areas. At this information centre, monitors will provide information about the natural monument and help you to plan your visit.

Here, you can find information about the signature species and habitats, to help you identify and appreciate the cultural and natural heritage in a respectful way. It promotes the conservation and appreciation of biodiversity and cultural heritage.

Leaving the car park, follow the wooden path to the Visitors’ Centre. Before you get to the visitors’ centre, there is a deck with an informative sign to the right.

The Ojo de Guareña Visitors’ Centre is in Quintanilla de Rebollar, an area in the Merindad de Sotoscueva municipality, which had 50 residents in the last census. It is said that the history of Quintanilla del Rebollar was forged by battles between the Cantabrian people and other cultures, including some of the Christian Kings who fought Muslims over peninsular Spain.

Some of the points of interest in the municipality are the Quintanilla de Rebollar church, with a valuable altarpiece inside, the old fountains and the San Bernabé cave chapel.

Before you come to the centre, there is a post off the path, which has detailed information on the Ojo Guareña natural monument.

Ojo Guareña is a complex karstic formation with more then 110km of passages across the Merindad de Sotoscueva, Merindad de Montija and Espinosa de los Monteros municipalities. It was named a natural monument by the Castilla and León government in 1996. The caves were formed out of carbonate materials from the Coniacian age, and they are on a stratum made of impermeable marl. Until the new parts of the Mortillano system were discovered in 2009, Ojo Guareña was considered the largest karstic system on the Iberian Peninsula.

The lines of the hills and summits stand out in the landscape. They are locally called the shells and they have been crossed by the Trema river and the Hoz stream through canyon paths. On the other hand, the Guareña river does not cross over the hills, it goes underground via a sinkhole named after it. This starts a path that is tens of kilometres long through the dark subterranean world in Ojo Guareña.

The last sign on this side of the monolith is about the surprising and extensive subterranean world in Ojo Guareña.

The second side of the monolith has a map with different trails to explore, as well as detailed explanations on each one.

The third side is about the network of nature areas in Castilla and León, showing a map of all the provinces. Castilla and León is one of the largest regions in Europe. It has rich biodiversity and landscapes within its 94,000km squared area. To preserve this natural heritage, the Network of Nature Areas in Castilla and León was established in 1991. It is known as the "REN" and is made up of 33 protected areas with an area of 820,000 hectares. This network highlights the ecological, geological and landscape values.

Right below the map, there are photos showing the beauty of the Las Merindades region.

Follow the path to the centre. A couple of metres before you come to it, there is a hut.

To the left of the path there is a hut with wooden walls and a metal mesh front. It has some stands inside with dry leaves, logs, pinecones and bricks on shelves, each one with a photo of an animal.

Continue on the path until you come to the Visitors’ Centre.

This information centre on natural heritage is located in the building which used to be the old Quintanilla del Rebollar school. It was built with a generous donation from Domingo Fernández Peña, a rich man from the town who made his fortune in Cuba. In 1919 he donated 400,000 pesetas to the town for the school to be built for the kids in the town and surrounding areas.

The building is divided in two parts: the lower part, where classes were held, and the upper part, made up of two towers where the teaching staff and their families lived. They are separated by a charming Latin-American style interior patio.

Throughout its history, the school was used until the rural flight when it was abandoned and fell into ruin. In 2005 it was inaugurated as the visitors’ centre, thanks to investment from the Castilla and León council. It has turned into a place full of information about the Ojo Guareña Natural Monument.

Now, go into the centre.

Inside is the reception desk and the green shop, where you can buy local products and souvenirs.

After the green shop, there is a staircase leading to the top floor and then a corridor.

Opposite the stairs, there is a tactile model of the visitors’ centre which can be taken apart.

Further to the left, there is an access point, labelled "Cube room".

Go inside.

The cube room is rectangular with a cube covered in panels in the centre. When you come in, to the left, there are sofas against the wall, under panels showing photos and information about the Obarenes Mountains-San Zadornil Nature Park.

In front of the sofas, there is a small table and a drinks machine in the corner. The right wall, as you come in, has a window overlooking an interior patio.

This same wall has a map of the Network of Protected Natural Areas in Castilla and León, with different colours showing the different categories of protection: protected landscape, the nature reserve in orange, the nature park in yellow and the natural monument in blue.

In the Las Merindades region, which covers almost a third of the Burgos province, there are four Protected Nature Areas: The Hoces del Alto Ebro y Rudrón Nature Park, the Obarenes Mountains-San Zadornil Nature Park, the Monte Santiago Natural Monument and the Ojo Guareña Natural Monument, where you are right now.

The historical origin of Castilla is in Las Merindades, when the seven original Merindades de Castilla la Vieja gave rise to the primitive Castilian county. The region is part of the Cantabrian and Ebro drainage basin, meaning it has a transition climate between the Mediterranean and Atlantic climates, although the Atlantic is predominant here.

Natural Monuments protect archaeological findings, karstic areas, caves and passages, as well as flora and fauna.

Go over to the cube in the middle of the room.

The cube has panels with photos and information on three sides.

Side 1 has detailed information about the elements that make up the Ojo Guareña. It covers the flora, fauna, geology and landscape, as well as the uses and traditions in the region. Representative ecosystems are highlighted, such as the Gayangos and Antuzanos lagoons, the deciduous beech forests to the north, and the oak groves on the limestone slopes, known as Seven Shells, due to the transitional nature of the region.

Related to the information about the landscape and uses of the land, the San Bernabé cave church stands out, as well as the mountain houses and stately house. This region, characterised by its climatic transition, influences the vegetation, fauna and local traditions. The ‘Pas’ influence in the valley is reflected in the style of the houses and the livestock practices.

Seven Shells, also called "seven rocks" or "seven sisters" is a long and highly protected mountain range, with two periphery areas of protection:

The second periphery protection area covers the towns and mountain in the region.

The periphery area of protection 1 goes beyond the Seven Shells. This area stands out due to its rivers and streams in the highest areas, which then flow down to the shells and flow to the karst, entering the caves. It is essential to keep this water clean and this is done with filter systems in each town before it reaches the high protection area. Dumping is prohibited and use of environmentally respectful products is promoted by livestock and agricultural farmers.

Protection area 1 covers the caves and karst spring sector where the water returns to the surface.

Seven Shells represents the distinctive landscape in Ojo Guareña, where the mountain is made of limestone, which dissolves when in contact with eater, creating channels, passages, rooms and vertical caves.

Ojo Guareña’s uniqueness shines through in its caves, with a 110km structure distributed across seven superimposed levels. These caves are the fourth largest in Spain and the twentieth largest in the world currently.

The cube has an aerial image which shows the wide diversity of landscapes with varied habitats and species. To the north of the centre’s car park, the deciduous forest typical to the region stands out. It includes sessile oak, Pyrenean oak, beech, holly, birch, yews and heath, which is fundamental for the pollination of flowers.

In the Sotoscueva valley, meadows predominate due to livestock activity. Keeping milking and beef cows requires fresh pasture to feed them.

This lifestyle is closely linked to the traditional architecture in the area. The construction of houses depended on three factors: the livestock-keeping lifestyle, the climate and the use of natural materials like stone and wood. Houses were built for shelter, using oak, which is common in the area, and sandstone for the masonry of the better buildings.

The area also has numerous Roman churches with religious architecture standing out, particularly the San Bernabé cave church.

In the olden days, an extensive part of the cave, known now as the Town Hall Room, was used as a meeting place for the council. Until 1616, meetings were held outdoors, around a large tree called the Sacred Holm Oak. The agreements made under these old branches were strictly respected. However, this year they established the first documents of the region and the meetings, which were now recorded, started to take place in the cave room.

The cuts in the rocks of the gorge allows both diurnal and nocturnal birds of prey to cross through. In these areas, colonies of griffin vultures, Egyptian vultures, golden eagles, peregrine falcons, red-billed choughs, short-toed eagles and booted eagles are common.

Now, go around the cube to the right to go to the next side.

The second side explains the geology and hydrology of the area. Through these panels and photos, the karstic function of Ojo Guareña is detailed, along with the circulation of the water.

There is a model showing the stages, from the catchment of the waters in the valley and the precipitation in the mountains, to the infiltration through the Guareña river sinkhole. It shows the internal circulation of the subterranean rivers formed in the limestone, creating a network of passages and caves, and finally the Guareña river karst spring, which comes after it passes through a series of aligned cavities in the Villa Martín fault.

The karst spring is where the water re-emerges, 6km to the Southeast, there are three openings where the water re-emerges: El Torcón, La Torcona and la Torquilla.

The lower model shows a scaled version of approximately 30km of passages in the cave, highlighting El Dédalo oeste, the most complex section in the system.

On the panel, the cave passage is divided in 6 levels.

One million years ago, the ground was at level zero and the river flowed over it, creating the first level. Over time, the rock dissolved and eroded different strata, forming six superimposed levels.

Currently, the river flows through the sixth level and in 100,000 years it could create a seventh level.

Continue over to the other side, to the right of the second one.

The third side of the cube has data and images related to the caves. It covers the passages and geomorphological formations in them, like stalactites, stalagmites and flows. It also highlights speleological work that has been carried out, discoveries in the Ojo Guareña caves, cave art and the fauna living in the caves.

The panel represents different sectors like the Seven Shells, the rivers, the caves and the subterranean passages.

It shows various rooms, such as the Berta room, Edelweiss room, the passage with formations and the flooded areas.

Lastly, it shows animals inside the cave, both microscopic and extinct, shown in prehistoric engravings.

Keep going around the cube to the last side, to the right.

The fourth side of the cube has a panel with information about some of the birds of prey that live on the rocky cliffs in Ojo Guareña, all of which are covered in rock vegetation.

Birds of prey are characterised by their sharp senses and strong talons, playing a vital role in ecosystems. Their wide range of species is known for its adaptability and hunting skills. These birds occupy an ecological niche, living on cliffs and rocky areas. They significantly contribute to population control of rodents and other species, regulating the balance of the ecosystem. Many birds of prey have key roles in the food chain, they are indicators of the health of the environment. Their majesty and ecological importance mean that these predatory birds are an essential part of biodiversity and a symbol of the delicate harmony in nature.

This panel is accompanied by another one which has photos and detailed information about griffin vultures, Egyptian vultures, golden eagles, peregrine falcon and red-billed choughs. The right wall has another backlit panel with an aerial view of Ojo Guareña, showing the Sotoscueva valley and Cornejo, a photo with information about the oak grove to the south, two photos with information about the Sotoscueva valley which has Cantabrian influences in its riverside forests, and various photos and information about the Testigo de Cornejo mountains.

Leave the cube and go to the door with a curtain in the back wall of the room, near the window.

Go through the curtain and you will find yourself in a recreated cave, with walls and a ceiling which simulate a narrow limestone passage. As you move down this corridor, with nooks and crannies to the sides, you will see various interactive elements. The sign with hands next to them show the possible actions, like listening, smelling, exploring etc. The first one to the left is a viewfinder which shows the geomorphological formations in the caves. At the end of the three-metre corridor, you will come into a circular room with a closed door.

Inside the room, to the right, there is a corner with Neanderthal tracks on the floor which simulates limestone. In the middle of the circular space at the end of the cave, there is a circle on the floor connected to the ceiling by a column made by a stalactite connected to a stalagmite. These formations are represented on the floor and ceiling of the circle. You can also see a small limestone bowl with simulated water which lights up when you touch it, showing a face at the bottom of the water.

The flows are on the walls of the cave and above the closed door of this final room, there are various bats on the wall. In the Ojo Guareña caves, 17 different bat species have been catalogued. The ones shown here are lesser horseshoe bats, named as such due to the shape of their nose.

You can also find invertebrates in the cave, such as daddy longlegs, a type of spider with disproportionately long legs that can measure up to 12 centimetres.

Beside the viewfinder, there are carvings of animals on the wall, with the characteristic style of cave paintings, outlines, with anthropomorphic figures and deer with large antlers.

Once you have explored the cave, go through the curtained door to the laboratory.

The laboratory has some metal worktops against the walls. Along the wall, there are photos and detailed information about the cave-dwelling animals in Ojo Guareña, including endemic species.

When you go into the room to the left, you will see a representation of a cave wall with a flow, near the first interactive element which consists of a viewfinder where you can see cave-dwelling animals.

Along this first worktop, which extends to the corner, there is a second interactive activity. The second worktop focuses on the geology of Ojo Guareña, with perforated plaques which represent the level curves of the ground in a cave.

The last worktop has tracks from our ancestors. Here, there are stamps, paintings and leaflets where visitors can recreate the cave paintings in the Ojo Guareña caves. At the end of this worktop, there is a panel with moving parts which have names on one side, and drawings related to the periods on the other side. There is a pedestal with sandstone and flint in the middle of the room.

Go to the first worktop, to your left.

Here there are various investigative studies performed on Ojo Guareña since 1960 presented. They have identified almost 200 invertebrate species inside the caves, many of which are unique in the world.

These studies come from a collaboration between the Spanish National Research Council, the National Museum of Natural Sciences and the Castilla and León council. They cover invertebrates inside and outside the cave, both terrestrial and aquatic.

These invertebrates, mainly crustaceans in Ojo Guareña, are particularly sensitive. In one photo, you can see some small carideans on a microscopic level. These crustaceans have different characteristics than those found elsewhere. The ones in the cave are millimetric, lacking pigment, with highly developed appendages. They are blind and highly sensitive to pollution in their environment.

It is essential to preserve their environment in order to ensure that these unique crustaceans, such as Iberobathynella guarenensis, do not disappear.

Ojo Guareña stands out world-wide for its level of biodiversity, thanks to the abundance and uniqueness of its invertebrates.

Now, go to the next worktop.

Ojo Guareña started being explored in 1956, and it continues to this day.

The pioneers of this effort were Gregorio López and Isidoro Bocanegra, with the latter being the parish priest of the cave’s municipality. Together, they were the firsts to cross the initial stretch between the Palomera cave and the Dolencias vertical cave, establishing the exploration bases. The exploration was professionalised by the Edelweiss Speleological Group, which took on the responsibility of exploring the 110km of caves.

They carried out studies on paleoclimates which analysed the climate changes in the last 3000 years through studying the growth of stalagmites. This analysis continues nowadays.

Now go to the third worktop.

This worktop covers the archaeological investigation in Ojo Guareña, showing 70 different archaeological findings. Among there are:

Bare footprints from 4,200 years ago, different shrines with cave paintings, like the "Sala de Las Pinturas" which is approximately 13,000 years old, burial sites and remains from explorers in the Iron Age who died inside the cave, the Prado Vargas archaeological findings which have vestiges from 50,000 years ago which correspond with the Neanderthal occupation of the cave. They found herbivorous and carnivorous animal bones, lithic hunting tools, as well as a premolar tooth from an 8-year-old Neanderthal girl, which was found in 2019.

They have also found flint chips, flat axes, bones used as gravers, spearheads and a jawbone from a cave-dwelling bear that is approximately 46,000 years old.

One of the most important findings is the Iron age explorer site.

In 1970 an archaeological site was discovered inside the Ojo Guareña cave. During an exploration in a labyrinthine passage know as "Vía Seca", an explorer found a skeleton. Beside the skeleton, they found a belt and an old fibula, used as a belt buckle. They also identified a stalagmite surrounded by a considerable amount of clay, suggesting that it may have been used as a water reservoir until the individual died. The skeleton was later moved to the Burgos Provincial Museum.

Go to the pedestal where you can touch the stones inside.

On the sides of the pedestal, there are details about the stones making up the base.

Now, go to the second pedestal, next to the entrance wall, between the entrance and the exit.

The second pedestal displays the representation of an archaeological excavation.

A door to your right, on the third wall of the room, leads to the audiovisual room and toilets.

The audiovisual room is on the left of this corridor and the toilets are to the right.

Between the two toilet doors, there stand with various wooden logs.

The Visitors’ Centre invites you to enjoy a 12-minute video, created by Javier Trueba in 2005, which captures the fundamental characteristics of this environment, presenting spectacular images of the inside of the karstic complex.

One the video ends, leave the audiovisual room.

Now, make your way to the first floor. To do so, go to the reception area.

To the right of the desk, there are stairs leading upwards, or if you prefer, you can use the lift to the left.

Once you make it upstairs, there is a corridor with the Memory Corner. Here, there are old black and white photos donated by the residents of the area.

After the photos, the corridor widens and there is an interactive panel, also within the Memory Corner.

In the middle of this wall, there is a ledge with a big red button. Press it to start the interactive activity which shows an older woman with a suitcase standing on a platform at a train station.

Continue to the room at the end of the corridor.

This column imitates the texture of an oak trunk and when it reaches the ceiling of the tower it opens with green sheets imitating branches. Each branch has the name of one of the towns in the Ojo Guareña natural monument written on it.

The room is vibrantly lit by the sunlight coming in the windows.

Here is where seasonal exhibitions are shown.

To your right as you come in, there is a two-part staircase and a landing which leads up to the viewpoint. The viewpoint is an interior balcony which encircles the seasonal exhibitions room. The windows look out the four sides of the tower.

his audio track ends your visit to the Ojo Guareña Visitors’ Centre, which highlights the uniqueness of the centre, its landscapes, the richness of the fauna, flora and orography which create a unique and idyllic ecosystem, and which also reflects the local products and traditions.

To leave the centre, go down the Memory Corner corridor and back down to the reception area.

If you would like more information, you can go to the display at reception or talk to any of the centre’s collaborators.

Thanks for your visit.