The Megalithic tradition of Nias is a living Megalithic tradition as a result of the cultural development that has been going on since the prehistoric period. The Megalithic tradition was introduced during a period between the Neolithic and Palaeometalic. Research on Nias Island was carried out at Bawömataluö Site, which is administratively located at Bawömataluö Village, Fanayama District, South Nias Regency, North Sumatra Province. The problems discussed here are the morphological unit that formed the site, stratigraphical sequence, geological structure, and the source of raw material to make Megalithic objects. The aim of the research is to understand the geological condition of the natural environment of Bawömataluö Site and its surroundings. Geological survey, petrology analyses, and interpretation of geological map are the methods used. The results show that Bawömataluö Site is situated on the slightly wavy morphological unit, which was shaped by Lelematua Formation. Observation on the geological structure reveals that Bawömataluö Site stands on the uplifted part (block-hanging wall) of a thrust fault. Regarding the source of raw material to make Megalithic objects, observation reveals that the stones were taken from Batubuaya River, which is 1.5 kilometers to the southwest of Bawömataluö.