Portugal is a very underrated and not well known country at least from what I've seen in pop culture and the media in general throughout my 55 years. Your book and video gave me chills confirming you've stumbled on what appears to be a new and mysterious world that needs to be seen by a lot of folks to be appreciated.
I've never heard of Sintra or Regaleira. I now wish I could afford to travel there. Maybe I could get a KS account going to fund it.
Several years ago I befriended an 80 year old former Las Vegas black jack dealer Portuguese woman neighbor in my apartment complex and found her to be a spitfire, engaging personality but with an old world charm who spoke with what I had to assume was a Portuguese accent. It wasn't Spanish, Mexican, Italian even though it sounded similar but I could sense an ancient, a bit primitive kind of royalty and wisdom to the tone that kind of is reflected in your images and in the video.
Wonder why I don't hear a lot of news out of Portugal in the media? It's always about the middle East, France, England, Italy, Japan or Israel.