According to some studies, the depletion of natural resources had brought about an ecological crisis and the decline of the ancient Rapa Nui society by the 16th century, which led to decline and to the spiritual transformation in which these megalithic monuments were destroyed. The original cult of the ancestor was replaced by the cult of the man-bird, which has as exceptional testimony the ceremonial village of Orongo, located at the Rano Kau volcano. Fifty-four semi-subterranean stone-houses of elliptical floor plans complement this sacred place, profusely decorated with petroglyphs alluding to both the man-bird and fertility. This cult would see its end in the middle of the nineteenth century.