There's a plastic pipe with a vent cover in my back yard that runs to a green cap in the middle of the yard. What is this for? I don't have a septic tank.
Update: this picture shows the entire length of the pipe that I'm aware of. The green cap from my second picture wasn't visible from this angle so I marked it with the piece of cardboard.
Based on everybody's comments, I felt comfortable digging it up. Here's the entire thing:
Thanks for all the help everyone! Your comments/answers let me dig up this unused nuisance I've had to mow and trim around for far too long.