This may belong under the Nautilus, but it is a separate rock 200ft to the east of it, near the Torpedo Tubes so I listed as a separate area.
Getting There
Walk along the south face of the Nautilus, past Friday the 13th to a point just before the Torpedo Tubes. Continue walking a few hundred feet to the east to the rock. All four routes face the Torpedo Tubes on the southwest face. This small formation has a massive, geometric boulder sitting on top of it known as both Exfoliate Boulder and Diamond Rock.