The large "keyhole" piece could be out of granite, mortared flagstone or cast concrete.
Stone would be very expensive, but would be very impressive. Flagstone or concrete
would be more cost effective. I don't know about the masonry costs, but the concrete
version would run around $15-16 thousand. That would include design, fabrication and
installation. It would not include the flagstone patio, iron railing or any landscaping.

                                                                                                                        Peggy Guest