At the most basic level, a cairn is a pile of rocks. But this definition doesn’t do justice to the myriad shapes and sizes of cairns found around the globe. Nor does it convey the many reasons that people have piled up stones for thousands of years, according to Seattle freelance David Williams. Cairns can indicate a trail, mark a grave, serve as altar or shrine, and reveal good hunting grounds and territorial boundaries. Before we all started carrying cell phones or GPS units, cairns provided a timeless means of communication. They say: “You are here. You are not alone!” Weaving together natural and cultural history, Williams’ book takes a thought provoking approach to exploring the stories of cairns from around the world. He shares tips on what type of rock is best for building cairns, how one can transfer fatigue to cairns, why an orange lichen-covered cairn indicates that some animal spent quality time on a cairn, and where to find ribald poetry hidden in cairns. He concludes cairns are enduring messengers in stone.