I'm American of Irish descent and have spent a lot of time in Ireland. The walls mentioned were sort of an academic trick. They had to do "work" to get "paid" and so they were made to just build walls so that they could then be paid in food and not starve.

If you hike around and see them, it's stunning. They were handmade. The rocks weren't insitu, they were carried in. It's not the pyramids, but in a relatively contemporary time they were made rather than just providing assistance.