Due to conservation reasons further details are not  public.
For scientific studies a password can be obtained.

For password protected version click here: Cueva de las Breñas o Túnel del Viento

Cueva de las Breñas  is situated near to las Breñas, Yaiza. It is a typical lavatube system with a lot of mysteries. The tube consists of large scale  karstic features. Calcite can be found on walls and floor as if a river  has been flowing through the cave. Karstic phenomenons like disks and pillars can be found. Depending from the wind outside and the temperature there can be quite some wind on some places. Cave consists labyrinthic by-passes and side galleries. Lott of long crawls and low passages.
Sand can be found in the cave and in the downstream part (east) in one gallery there can be found heaps of shells (falling in from above??). Dripping lava formations like stalactites and stalacmites can be found in some side galleries. 
Cave is still under exploration. 
Cueva las Breñas is probably the biggest mysterie on the island relating to age and morphologie.