A "grotto" in the bluff along the creek on the east side of the property. You can't really tell from the picture, but there's a spring at the top dripping off the edge, as well as several others in different places on the rock face falling into a small pool at the bottom which then flows out into the creek.

Its a beautiful spot, but REALLY brushy (hence the close-up shot, since you couldn't see it through all the scrub from any other angle.)