I don't know what this goes to I tried to turn it but the handle just bent cause it is soft. It is a pipe that goes down i dug about a foot inside the pipe, but nothing at that depth. the pink cup you see is the cleanout for the wast pipe, The gas line goes into the house on another side, so i know it's not that. Thinking maybe a shutoff close to the house? but that is sure close to the wast line. Idk there's a shutoff already at the water meter.
That looks like a shut off for an older water line. Many times u find that on galvanized water lines. I would avoid turning it. If u do it may have a weep hole in the ground that will drain the water from your mainline.