Four Walls

I blipped a bit of wall a few days ago that runs along a short road through the local golf course.  The golf course, and all of Orkney, has a lot of similar walls but if you study them you can see that they are of varying ages.
1. Is a recent section and it looks like a budget version.
2. Is one of the beautifully neat ancient parts that pre-date the golf course.
3. Is what happens when you play Jenga with an old wall - there is only so much it can stand.
4. Walls within the village of Skara Brae - at least 5,000 years old and still standing.