if you go on Pinterest, you can find several ideas!!
A Tree Stump type Log, place Wagon wheel. Drill into stump to secure wheel. Buy Safety Plate Glass approx 4" dia. larger than the wheel and place on top.
Hope that helps.............Enjoy!
Joanne, My dad did the same as Johnavallance suggested, but he added a 1/4 inch plywood under it so he could place arrowheads and other rocks from his collection under the glass. It made a wonderful conversation piece.