Sima de la Raja

Sima de la Raja is a vertical karst cave in the municipality of Villanueva de Alcorón, in the province of Guadalajara, inside the Alto Tajo Natural Park. This is a destination for people drawn to real caving rather than a paved-path attraction — reaching the inside requires speleological gear and basic rope-descent technique.

What is this place?

Sima de la Raja is a karst shaft roughly 90 metres deep. Its entrance is a narrow fissure in the ground, easy to spot thanks to a tree growing right beside the opening. The first stretch is a vertical shaft about 45 metres long, wide near the surface and narrowing as it descends. At the bottom of this first drop, a stone ramp leads to a side chamber filled with dripstone formations — stalactites and other rock structures shaped over thousands of years.

In 2018, the Castilla-La Mancha Federation of Speleology and Canyoning selected Sima de la Raja as the second "school sima" of the Serrezuela de Valsalobre, a site set aside for training vertical caving techniques such as rope descent and ascent. It should not be confused with the nearby Sima de Alcorón, a much more accessible cave roughly 63 metres deep, fitted with 207 steps and handrails and built for ordinary visitors who do not carry climbing equipment.

How to get there?

Sima de la Raja is reached via the CM-2101 road linking Villanueva de Alcorón and Peñalén. About 600 metres before the Refugio de la Zapatilla recreational area and the entrance to Sima de Alcorón, an unmarked track branches off toward the cave opening. The route runs through the Alto Tajo Natural Park, so a good map or GPS device is worth carrying — the entrance is not visible from the road and is easy to miss.

What should you know before going in?

Descending into Sima de la Raja is a technical activity that calls for proper preparation: harness, rope, carabiners, and the skills needed to move through a vertical cave. This is not an outing for casual visitors without experience, unlike the neighbouring Sima de Alcorón, which has fixed stairs and lighting. Anyone interested in the region's karst landscape and geology without wanting to rappel is better served by that second cave, or by the scenic hiking trails nearby in the Tagus valley.

When to visit?

Spring and autumn are the best times to come, when surface temperatures are mild and the cave interior stays at a constant, cool temperature year-round regardless of the season. In summer it is worth avoiding the hottest hours of the day on the approach to the entrance, while in winter the access track can be difficult after rain or snow.

Frequently asked questions

Can you enter Sima de la Raja without caving experience? It is not advisable. The descent requires speleological equipment and technical skill — the first stretch alone is a vertical shaft nearly 45 metres deep.

How deep is the cave? Sima de la Raja is roughly 90 metres deep, with an entrance shaft of about 45 metres leading down to a chamber filled with dripstone formations.

How is it different from Sima de Alcorón? Sima de Alcorón is a separate, nearby cave that is far easier to visit, fitted with 207 steps and handrails, and suited to ordinary visitors without climbing gear.

How do you find the entrance? The opening sits just off the CM-2101 road between Villanueva de Alcorón and Peñalén, about 600 metres before the Refugio de la Zapatilla — recognizable by its narrow fissure in the ground with a tree growing beside it.