Kirkjugolf looks like a man-made stone floor set into the grass, which is exactly why it picked up the name "church floor". In fact it is the top of basalt columns, worn flat enough to resemble paving.
It is a small protected natural monument, not a long stop. That is part of its charm: two minutes from the road, a few minutes on foot, and you get one of Iceland's neatest geology tricks without a crowd-control machine around it.