Account of the 25-year excavation program of the ceremonial center: great mound with two back-to-back passage tombs and hundreds of stones elaborately carved with abstract motives. Smaller sites cluster round it and the whole complex is discussed in the Irish context. Cremation was the rite, but a whole society's beliefs are encompassed here. Skill is seen in the selection of building materials and in the understanding of how to counter stress effects in corbelling. Much environmental material. The Irish contribution to Scottish passage tombs is stressed. -- AATA