Granted, not all of them are the work of Mother Nature. A couple of them are man-made and quite a few are an amazing mix of art and nature. Then again, we're part of nature, too.
Which of them have you seen with your own eyes? Which do you want to visit (well, all, unless you're a monster, but I mean first)? Which would you chose to live in?
I've only been to the sea caves here in Portugal and, before seeing this, the Travertino Pools in Turkey were my next dream destiny, but now I'm thorn between the Isle of Skye in Scotland and the Bamboo Groove in Japan. ^__^