Err....I’m not making this up.
Part of the wall can be seen in the middle left. It goes behind a large cairn which rises to the same height of the wall but is completely separate from the wall. The cross marks a place where the Blessed Virgin Mary (it is claimed) has been making regular appearances.
borgin-nadur.blogspot.com/
Image credit: E.R.
Multi-phase monument then?
It doesn't make sense. You don't build a defensive wall with a cairn just a few feet away overlooking the wall. So the mound must be non-prehistoric (?). So why is it there? Buggered if I know.
The cairn is very lumpy - looks more like a spoil heap, or perhaps rubble from another part of the structure that included the wall. Is there any mining or anything in them there hills? I agree with you that you wouldn't build a "defensive" structure where someone could just walk up the cairn to wall-height and chuck spears and arrows at you. Hmmm.
Does the construction of the cross give any clues as to age (is it made out of MDF, for example)?
All I know is that there's a magnificent Bronze Age wall with a more recent cairn next to it which is visited by the Virgin Mary (apparently) and hundreds of Catholics. The Bronze Age wall gets much less attention.