The Soft Room is seen in the Season Fifteen episode, "The Poor Kid". This is a quiet room in the Police Station. It is a room designed for kids to feel safe in, however, it is full of disturbing images of clowns.
Background
Kenny, his brother, and sister wait there for social services from Mr. Adams after they had been taken away from their parents. Cartman is also sent here after he gets his mother arrested.
South Park: The Fractured But Whole
The room serves as the start point for the Scavenger Hunt: The Headshot Job mission.