This small boulder is located in the Morter rock city park back and left of the main wall. It is about 15 feet tall and slightly overhanging in the middle bulge of the rock. You know, it looks like half dome, wonder how it got it's name.
From Mortar Rock proper, head left and momentarily downhill about 30 feet on the further out path. This will take you to the "entrance" of the park. Continue heading on this trail uphill another 30 feet, and it's the fifteen foot high rock that looks like half dome on the left side. Can't miss it.