This cache is one of those experience in Madeira.
Attention: The cache is inside the tunnel, don't look outside for it!
To do it, just prepare yourself with:
Confortable walking boots
Flashlight
Hard Cap (watch your head) 
A camera
A pen to log (just in case)
Beware:
Don't do it alone
Inform someone where you intend to go because in this area no cellphone network is available
We don't advise to do this in Winter time or in rainy days, could be slipering and dangerous in some parts
About the cache
Is a regular box that can handle some trading items.
Take some time to cover the cache as you saw it or better, don't do it in rush!!!
Warning: If you reached the final tunel coordinates is because you already pass throut the cache.
GOOD LUCK, (You'll need it!!!)