Hmmm. By design?
From what I can tell, the three pillars are supposed to mark the spot where Satan tried to dissuad Ibrahim from the sacrifice that he was going to make of his kid. They later came to symbolize the devil.
Which is a further contortion if the event based on but not quite duplicating the earlier religion of Judaism. Interesting that in the muslim case the emphasis is on the devil's alleged attempt to prevent his from making the sacrifice.