On Friday, I was walking back from lunch with Christine when I noticed a small plaque embedded in the sidewalk, just outside the Northernmost entrance of Chase Tower. The message is carve into metal, and embedded into the sidewalk. The text of it reads:
Spotted this on the NW corner of Jackson and Clark, downtown Chicago. Assuming it’s something for wintertime, to prevent ice from building up… but in all my years living in the city, this is the first time I’ve seen any kind of sign like this.