The magnificent Nerja Caves – Cuevas de Nerja – are a series of huge caverns stretching for almost five kilometres and home to the world’s largest stalagmite, a 32 metre high column measuring 13 metres by 7 metres at its base. There are three Galleries – Show Gallery, Upper Gallery and New Gallery – with each gallery containing a number of Halls. The Upper Gallery and New Gallery contain many of the prehistoric cave paintings, but tourist access to these areas is limited to special groups.
Here can find more information: https://www.thenerjacaves.com/

And how getting to Nerja’s Caves: https://www.thenerjacaves.com/getting-there/