Cedar - So we had to cut a very large tree down, so instead of turning it into fire wood we turned it into a patio. We love it. We used inch slabs of western red cedar, laid on a base of rock and sand, with inch crushed rock in between.
I love this idea for putting posts up, for lamps, that can also be fence or divider connectors. I like hiding a sturdier metal post inside a fabricated wood post, then attaching the remainder of the fencing to it. Great for high wind areas.