One is at the beginning, where there is no exhaustion and no sleep. That Wall is where we start, the Wall of Birth, and most of us spend the majority of our lives between this Wall and the Wall of Sleep. You can approach it through exercise and newness of experience, but I doubt we can ever actually reach it. Approaching this Wall brings you into contact with feelings of childlike wonder, giddiness, and joy. Hovering near this Wall are characters like Peter Pan and sacred fools.
Approaching this Wall holds some fascination for us. We know what is near this Wall: A less complicated time, a place where wonder and life were new and interesting. Longings for childhood or "the best years of your life" are symptoms of looking at this wall. We look at people who are closer to this Wall than we are, and they seem full of life and love and happiness. Little do we know that they look at others who are closer to the Wall of Birth with just as much envy as we do them.
Initiatory experiences can bring one into contact with this Wall, but they're more likely to push you against the second or third Walls.
At this time, I'm not sure what would happen if you broke through this Wall.