In this clinical paper, I present the development of the foundation of a child psychoanalytic treatment to explain in clinical terms what it means to build a “playground,” a place where a child could go to play. The aim of the paper, with references to Paul Street Boys, a famous novel by Ferenc Molnár, a Hungarian contemporary of Sándor Ferenczi, is to use the metaphor of the “playground” for describing how, thanks to his personal use of the setting, and thanks to the development of the relationship with the therapist, a traumatized child could gradually begin to build, together with the therapist, a place unknown in his past.