Thank you! I guess my memory was embellishing just a little and now that you mention it I do of course remember that it was a sign in the shape a Lava Lamp. I guess it said "Lava Lite" across the top or the bottom. No way an operating lamp would have survived a Chicago winter! Besides, a giant Lava Lite outside would have attracted chemically stimulated people and I don't rember ever seeing any observers sitting on the sidewalk-or ever being one! It was just so cool and just a little surreal to go by a large building that had a giant version of such an iconic object sticking out of it. I think it had to be 20 feet high.