The Keyhole Sink Petroglyphs is a site between Williams and Flagstaff, Arizona that we haven't visited yet. The petroglyphs are located at the end of a short hike from an official trailhead along Old Highway 66. For turn-by-turn directions you can enter 'Keyhole Sink Trail Arizona' into your driving app. If you are coming from the direction of Williams it will probably have you take I-40 Exit 171 to get onto Route 66. From Flagstaff it will probably pick Exit 178.
Included with this post is the GPS file and map that we plan to use for our first visit. If you don't want to wait for us to get around to it feel free to try the GPS file and map for yourself. With no guarantee, of course, but they most often prove valuable for us.