That's what I call it. Apparently the rocks slid down the mountain and landed in the river (George, is this the South Fork of the Potomac?) to form this unusual shape.
I look for the rocks whenever I visit my oldest son because the formation is right beside the highway. Saturday I saw the rocks in a new way--the sun was coming through an opening in the top of the rocks and illuminating them inside. The light reflected from the rocks and was dancing on the water and on the rock walls. It was so beautiful.
I tried to capture the light in a photo but some things just can't be put into a still picture--like rippling, glinting water and rock.