The walls are staircases down to a well. Not suitable to my local geology, unfortunately.
I find it hard to resist clickbait like "20 places you didn't believe could exist." Here's another, a fairy-home in Romania. Lately there's been a rash of links to eye-popping waterfalls in that part of the world. You have to wonder how this one didn't show up in the Lord of the Rings:
China is unimaginably big and various. If this site were in the West, we'd have been seeing images of it more often than we see the Grand Canyon, but it's a first for me: