Under the Q.E.W.
It was near the doctor's office and he lived down the street. It was the easiest shortcut to get from one place to another, first the doctor's office, then later a job at Chapters. His mother enjoyed walking and took him there, but later told him it might be dangerous for him to go by himself. He would mainly come to hang out.
This is a place he would come before he had a car. After owning a car, there wasn't really a need to go there. In the time since he'd been there the graffiti has become more elaborate.