Near Barro a limestone knoll stands out from the coastal plain. A stream sinks on one side of this, at Quintana, and resurges on the other. The stream actually sinks in a series of blocked sinks, but there is a penetrable cave entrance nearby. This we did not investigate, since Jim Sheppard cut his foot while crossing the stream (which was very polluted), and it was considered more advisable to return so that the wound could be cleaned and dressed.
The resurgence, the Cueva de Llera proper, is a fine cave entrance, which has been dammed to provide head for a water mill. About 30 m in the stream sumps, doubtless the effect of the dam.
This was a cave by the side of the road near Mere, which a local inhabitant informed us had no name (sin Nombre). He told us that it had been explored the previous year by some English cavers; on our return to England we found that these were the Nottingham University expedition, who had given it the name of Cueva Geoffo. We were unable to penetrate into the master system, since the water level was so high as to turn their "duck one" into a sump.
Near the village of La Borbolla is the source of the Rio de las Cabras, a very large and impressive resurgence cave. Some 20 m up the cliff above it is another entrance, in which the stream can be seen again. The underground course of the stream can be followed by a series of shake-holes and collapses, and some kilometres away a pothole gives access to the stream again. At the time of our visit, the system was in an extreme state of flood, and it was not possible to make any progress in any of these caves. It seems possible that most of the underground streamway is collapsed, but a further visit in dry weather is definitely called for.
The top of the Sierra de Cuera is a relatively level area of fairly rough karst, dotted with shakeholes which take all the drainage of the area. Several potholes appear to go to some depth, and to be worthy of exploration. The great problem though, is the transport of tackle. There are very few paths up, and these are very steep. The karst on the top is very difficult going. The only feasible method (short of using a helicopter) would be to use mule transport. The organisational problems would be considerable, since food and camping equipment for a stay of several days would be needed.