Along the Lands End Trail in San Fransisco there is an out cropping of upon which this labyrinth has been constructed out of stones. I'm not sure if this is maintained by the park service or just some sort of grass roots expression of ingenuity. It's approached after descending a steep side trail and, at least for me, was a total surprise. There were at least a dozen people working through this to reach the center. It sits atop a cliff overlooking the bay with a spectacular view of the Golden Gate Bridge in one direction and the pacific ocean in the other.