Ancient animal enclosures in DPRK?

I created the most comprehensive map of North Korea back in 2017 and I'm working on an even better version now.

In the process of that, I have come across a bit of a mystery. In two clusters, one in North Hamgyong Province and the other in Rason, are sets of large circles (roughly 240-250 feet in diameter) and webs of stone walls that create massive enclosures. I've been able to identify over 80 miles of wall and 21 circles.

Based on erosion, I'm pretty certain these structures pre-date modern North Korea and are very likely centuries old or older.

My questions are:
1. What are they?
2. Could the stone walls/fences be ways to corral animals toward the circular enclosures for capture?
3. Or is it to help protect animals while they're grazing?
4. Has anyone heard of them before and how old might they be? (they aren't exactly the same as desert kites, and they're not ceremonial stone circles)

Also, only small villages exist in these areas. The idea that a few dozen families got together to construct miles of wall in very rough terrain doesn't seem plausible.

However, a review of historic forts in the area shows that there used to be a substantial military population there. Perhaps these enclosure systems were built to help supply the various garrisons? Using thousands of soldiers to build the sites seems a lot more likely than simple villagers.

Attachments:

DPRK Enclosures.kmz (62.32 KB)

Here's a screenshot of the two enclosure sets and the multiple historic forts (white squares) in the area.

Bruha, what settlement name! - However hungarian language "undok" means "odious" in english, I wont hate this thread! (:


***
After doing some measurements (each from both groups are exactly 75 meters diameter) and considering the perfect shapes (also intact, straight walls), my first impression was that these must be not that old. 

About the function - well, these are very good traps of wild (also herded) animal. Driven by the walls the herds (groups) of animal easily can be lead to the circles, which however are not simple circles. As animal arrives to it sarts to run around until finding the gap. Then enters -in hope of hide- and being trapped with all of their followers.

If you check the southern group (East of Undok) you can note the walls make sections of land for the enclosures, also fence off settled (urban) areas. (Note, these are settlements of present days!).

About who built these, well... it does not really matter in a country where "each citizen is a good soldier of the system".

***
I think what we see is some kind of a wild farming or herding system from the 1960's - 80's, that might have not fulfilled the requirements so let abandonded. (Hopefully engineer could got away execution.)
Probably somewhat older, but 20th century constructions I would bet.

***
I have never seen such before so all these only a theory by me. Sorry I bully your archaeo-concept, but if these were ancient structures we should expect wider geographical occurence and would find them also outside the todays borders of North-Korea. (Or at least at other sites than these two sets.) Do not mention, if these were such old, then would be look more worn I think.

Of course, I bookmark thread in hope of the sequel! (;

Best!
G