This just popped up again on the new City Planning Commission blog Philadelphia Planetto. I had seen this illustration long ago, but hadn't been able to find it again until now. As part of the formerly-proposed Crosstown Expressway, we would have had a 6 square block underground parking garage, spanning 13th to 15th Streets, from Spruce to South St. Ugh!!!
Thank Goodness This NEVER Happened: The Crosstown Expressway | Philadelphia Planeto