This past summer we put in what I like to call a 'Tricycle Track' that wraps around the front lawn for the grandkids (and sometime big kids) to race around. It is a four foot path that allowed me to replace a good part of the lawn with another material that does not require water and still keep the family that loves to play on the grass happy. It is simple D.G. (disintegrated granite) that it tamped down to make a solid surface. At least until it rains and the worms below start to do their thing.
In the picture is a portion of the path and it is usually very clean and that lovely golden beige color. When it rains it becomes littered with dark little piles of soil from the ground below where the worms push through to come to the surface for air. Once it is dry the path can be swept clean and will once more look the way it should.
This is a great way to demonstrate the important role the worms play in a lawn to ariate the soil (in addition to many other advantages). I've read that a healthy soil was 17 worms per square foot. After two years of organic care for this area I would guess I'm approaching that number. What encourages worms? Organic material for them to consume. What diminishes them? Chemicals and an occasional early bird. Organic lawns do not require thatching or airating. Let the worms do it for you!