Trichocereus chiloensis... ?????????? As a guess

or try Echinopsis types

Nice find

PS Feel free to visit us in the Reg Cactus & succulent forum posting here is by chance that it gets seen

Here is a link that might be useful: If you this already then just incase

Thanks for the link, yes I know of this site.

Not a Chiloensis, spines on my cactus are much too thin and flexible to be chiloensis. (I own a T. Chiloensis).

I was wondering if it might be a huge gymno, but the fluffy-hairy remains of past flowers leads me to think otherwise. Gymno flowers are not hairy.(?)
Unfortunately I removed many massive fluffy clumps to see if it had bugs hiding. These clumps could have been good for I.D. (a little remains at the apex).

Waz