These piles of random junk have been stored, not so neatly, but at least organized enough so that when you look at the building from the other side of the columns, you can still get a nice clean picture.
Did someone intentionally clean up a mess left behind, or did the original depositor of these goods consider the best place to leave them? Of course, it could just have been to keep them out of any rain that might come. Or it could be completely random.
Who knows what really happened, but I think there may be some organizational tendencies at work, even if subconsciously.