Research on understanding Carnac alignments emerges periodically, as well as the definition of cairns which are interpreted as tombs and temples. However, there is no final conclusion or common agreement. This study draws new conclusions by deciphering the beliefs of megalithic people which are incorporated in their constructions and unveils commonalities amongst alignments, cromlechs and cairns. Three groups of keys drivers were selected to establish a conclusion: The beliefs of megalithic people concerning goddesses and ancestors, the alignments of stones, the semi-circles or circles of stones, the celestial objects sun, moon and Venus. Moreover, the relations with Shamans and similar beliefs in various civilizations as a legacy from megalithic people. The bearing of the stones’ alignments and cairns’ corridors, the angles at which celestial objects can be seen from the cairns’ chambers, and the time when sun light enters the inside. All this, in connection with the annual events of nature. Self-recorded data of the intensity of the magnetic field in some areas at Carnac in order to identify low intensity places which could be mapped to later Druid sacred areas. The study identifies: The orientation of corridors and alignments based on beliefs of Megalithic people, related to celestial objects Venus, the sun and specific moon phases. A sequence which is occurring every 8 years and concerns the visibility of the celestial objects’ configuration at specific bearings, as well as the period of year and time. The existence of bands of lower earth magnetic intensity at Carnac “Le Ménec”. The likelihood of specific locations on the sites where the shamans periodically conducted ceremonies. The results of the study highlight a strong link between the beliefs of megalith people and the triad of celestial objects the sun, the moon and Venus. The incorporated beliefs in all sites show a lot of commonalities which lead to define Carnac’s alignments and cairns as ceremonial, observatory and calendar sites.