Henge location?

I’ve been looking through some item browsers and noticed that some weapons have a really high spawn chance at a “henge” structure. I’m playing on a fairly recent experimental and have never seen one, so I believe it’s either extremely rare or just something that has been patched out and the item browser is just outdated. Any info on what it is and what’s there would be helpful.
(from what I can tell, the henge is a 3x3 map tile location, not the standing stones forest tile variant)