I'm not sure if this post will interest most of you. I happen to find the subject quite fascinating. Walking through the streets of New York, I often see strange messages and mysterious symbols scrawled on the city's sidewalks and walls.
This is a language spoken by the men and women of our nation's utility companies. Those who are able to read it can see under the ground--and perhaps even into the future. (For instance, the markings in the photo above indicate where a new street tree is about to be planted.)
The language is color-coded, making it easy to know which utilities are at work. (It will also give you a sense of where you might be able to find a sewer line in an emergency.)
Fortunately, it seems that no one knows who's behind the GOLD sidewalk markings that are sometimes spotted near the city's oldest buildings.
More at the Smithsonian. (Have a look around while you're there. It's a wonderful site.)