In January 2011, I decided to build an outside kitty play area.  The area is approximately 30 ft by 20 ft.  The walls are made of 8ft tall PVC fencing and roof is covered with netting brought in from Seattle Fishery.  I also covered half of the roof with shaded screen to keep direct sunlight from covering the entire space at one time.  My cats are allowed outside with supervision and the area is outside my bedroom window.  The entire area has a ZEN type feeling to it and is relaxing for all of us.