The caves were first discovered in 1959 by five boys who accidentally found access. Inhabited during prehistoric times, the caves had lain undiscovered for thousands of years. Now anyone can see them. Follow the highway east out of Nerja for about 2km -- it is well signposted and there is ample parking -- or take one of the may buses that run daily from the bus depot in the centre of Nerja.
Admission costs about 12 Euros ( May 2003 ) but it is well worth the money. Once inside , you descend down some steps and enter the caves. Huge caverns filled with stalagmites and stalactites, formed over many millions of years. There are many different caves to see and many of the rock formations are in peculiar shapes that , with a little imagination , can be made out.
Guided tours are available but we found it just as easy to follow the route ourselves. A word of warning for the infirm, these caves involves some steep steps and a, at times, precarious route so I would advise against those who are not surefooted.
The acoustics are such that concerts are still held there (one guide was serenading his group while we were there and it was amazing to listen to). The caves really are something you need to see to do them justice -- words cannot, in this instance, adequately portray the beauty and majesty of these natural phenomenon.