There is a large part of this story in “The Lost City of Z”.
Michael Heckenberger (mentioned in the article) was interviewed in that book and he showed David Grann some of these settlements.
Read Lost City of Z quite a few years back. I recall being quite engaged in it in the middle of the book. Nice plot arc, but I can’t remember the ending. I feel like I was disappointed. Didn’t he die at the end?