We spend hours and hours at the playground. My girls enjoy the novelty of the play structures and invent game after game to pass the time. The gravel is the most fun and has been used to build with, cover slides with, and poured into socks to sell at the make believe store.
I see how they have relaxed into being together day after day hour after hour. They collaborate, give and take directions and and then each go in their own direction to pursue some in individual task.