A weed and a mystery solved

Over in Ireland Park today, there were many of these, but I have no idea what they are (except "really ugly").  That's a normal dandelion in the lower left, for a size comparison.

It looks, if not tasty, at least edible, but that's really all I can say about it.

Also: mystery solved.  Those witch's hats must have been covering up the hardware attachments for the new benches they put in.  You can still see the cut-away along the back edge of the bench's supports.