From Stonehenge and the Ring of Brogdar to the Rollright Stones and Avebury, the British and Irish Isles are scattered with the stone circles of our prehistoric ancestors. Although there have been many theories to explain them, to this day there is no consensus about their purpose. Colin Richards and Vicki Cummings provide a clear and illuminating field guide to 424 key stone circle sites in Britain and Ireland. Organised by region, this volume sets out the features of these megalithic monuments, including their landscape position, construction, and physical properties. The authors take stock of cutting-edge research and recent excavations stone circles that were previously lost to time. They present new insights on the chronology, composition, and roles of different circles to transform our understanding the sites.