depressions in the sidewalks

On our way to the playground off of 7th and South Streets, Ruby concluded the puddles on the cobble-stoned pavement were made by melted ice. I said the depressions in the sidewalks gave them their shape. She asked, "Do you mean the sidewalks are sad?" I said, "No, but the pockets in them allow puddles to be formed." She responded that they are depressed "because of winter, probably, or that they can't play."