There are thousands of megalithic monuments - dolmens, passage mounds, menhirs and cromlechs - in Portugal from which the best preserved occurred in the eastern part of the country, almost all built of granitic rocks and on granitic hills, but they can also be built in shales, sandstones and limestones. These pre historic monuments have since always been an enigma: their religious meanings, the rituals of early man, and the manner in which they enigmatically interacted with their surroundings. The question is, what did these megalithic monuments represent in the lives of early man and what is their relationship to the landform morphology and lithology of the respective sites? How did rocks and landscapes condition the selection of these sites? This paper tries to explain the distribution of some megalithic monuments and heritage features in Portugal as a function of various factors, including geology, lithology, and landform development. After analysing the influence of the several geomorphological features on the choice of megalithic sites, we did not find any reason strong enough to explain it. Then another question was posed: which could be the real reasons for their choice? Radiesthesic methods can give a complete explanation for this even if the scientific community has not accepted them until today. This work tries to open a path for a new envisagement of science and for the bounding between science and parascience.