Furnished content.
(from Lumberjocks.com)
To test my recently built bowl lathe, I performed this project using a black locus endgrain slab. Due to the unbalance, the heavy lathe of about 1,700 pounds shook mildly even at ~700 rpm (my guess, no rpm reader equipped). After turning the concentric circles, two circles were cut into segments using a router lathe (last pic). Black lines on the other circles were made by grinder wheel. A reptile eye was imbedded at the center to symbolize the Sauron's eye located in side the castle walls. This slab had small decorative burls at the outer rim.