Geoparque Mundial UNESCO

Nº27 – Castañar Cave

Geoparque Villuercas > Nº27 – Castañar Cave


The cave is located on the road from Castañar de Ibor to the campsite, near the Interpretation Centre of the Castañar Cave .

The cave is an extremely fragile environment. For that reason it can only be accessed under a strict regime of visits. To access inside the cave (guided tour) it is necessary to apply for according to the procedure established by the Directorate General of Environment. See below:

The views set period of May 1 to September 30, 2015.
Requests for visits for 2015 will be accepted from April 1, 2015.

Application for entry into the Cave of Castañar
You must be registerd in a Guest reserve list. Access here to the information:
Alternatively it is very interesting to visit the Centre. This center have reproductions of the most characteristic speleothems, a virtual tour of the cave through a 3D projection, panels and interpretation of all geological features of the cave and its surroundings. You can find in this page an e-booklet with the English version of the interpretation panels.


Its great variety of shapes and its mineralogy make the Cueva de Castañar a karst cavity that is unique in the world:

Coladas: These are formations, generally of calcite, with thick layers that reach the ground in steps.

Flags or curtains: They hang from the walls like veils and are basically of calcite.

Ribs: Vertical formations with a tubular morphology that hang from the ceiling and have a central channel through which water drops. They are of aragonite or calcite.

Stalactites: Similar to ribs but larger. They are of calcite or aragonite.

Stalagmites: They grow from the ground where drops fall from a stalactite and have a calcitic and/or aragonitic composition.

Columns: These are formed by the coalescence of stalactites and stalagmites.

Fibrous formations: These are the most characteristic speleothems of this cave; they are acicular crystals of aragonite. They develop from a central point to form very delicate fibrous-radial aggregates which are known as “aragonite flowers” (this is the logo of the Geopark).

Moon-milk: A matt white globular deposit that may have a considerable content of intercrystalline water. The minerals from which it forms in this cave are essentially dolomite and magnesite.


The Cueva de Castañar has developed within the carbonated rocks of the so-called “Grupo Ibor”, which date from the Ediacaran (+540 ma). This cavity has been formed by the dissolution of certain magnesian calcareous rocks known as dolomites CaMg (CO3)2 and magnesites Mg(CO3) and by the consequent collapses or subsidence of the shales and sandstones located above the cave, which are arranged in fine layers. On the other hand, the network of cave galleries follows the same orientation as the geological structure of the area, and the morphology of the various rooms reproduces up to a point the “chest-shaped” form of the folds affecting these Precambrian rocks.

The fact that the cave has developed on carbonated rocks that are very rich in magnesium makes the water that flows within the cave also very rich in calcium and magnesium. This means that the speleothems or typical cave formations (stalactites, etc.) are calcareous mineral deposits such as calcite and aragonite (the aragonite/calcite pair was the first recognised case of mineral polymorphism; it has the same chemical composition of calcium carbonate (CaCO3) but with a different crystalline structure). Magnesian minerals are also present such as dolomite, magnesite, hydromagnesite, and sepiolite, which form part of the “moon-milk”.