Rodney,there is no treasure connected to the green circle you see in your grass,it is caused by a fungus.The circle is called a fairy ring.The fungus starts in the center of the circle ,usually in rotting wood.The mycelium (roots)of the fungus grow outward from the center ,getting larger each year.The green grass is caused by enrichment of the soil as the mycelium rots.If you watch you may see mushrooms along the circle during the spring.The dip in the center is probably from a rotting tree stump.Sorry to burst your bubble.