Mined cave (not clear if the start was a cave and afterwards mined)  near the parque natural (parque de jugar)  at Los Bolos, the radarshuttles near Haria.  Entrance to the cave is an awkward slippery path and steps down from the top of a cliff. Looking down a vertical wall of about 600m. height. The cave consists of several mined rooms with windowlike views onto the sea.
The material which is mined is a kind of brown/redish  gravel (picon).

Coordinates: 13*31’32.158″W 29*7’27.631″N

Here is a nice short film about the mine from Carmen Smith 2021