I went to Brazil a couple years ago and did a lot of looking for tunnels down there, even had my Brazilian girlfriend search Portuguese language sites. There is a Skyventure tunnel somewhere, probably near Sao Paulo, that is owned by the military but is rumored to allow the public one day a week or one day a month. I didn't have any luck contacting them. There was supposedly portable tunnel located at a dropzone outside Sao Paulo, but it had moved or was no longer operational by the time I got there. I plan to return to Brazil in December and will be looking in to it again, if I have more luck this time I'll make a post.