ABSTRACT
We present here evidence of pre-Portuguese presence in the Azores Islands, Portugal, found near the site of Grota do Medo (Posto Santo), discovered by Rodrigues (2013) in Terceira Island, Azores. This evidence was dated by Accelerator Mass Spectrometry, and indicates the presence of human activity in Terceira Island before or during the XIth century. The evidence consisted in a man-made rock basin, which was found in a site that contains also striking similarities with many other aspects from ancient cultures, including other man-made rock basins, arrangements of large stones which resemble megalithic constructions, and inscriptions in stones which resemble ancient petroglyphs. Although the dating of this evidence is highly suggestive of the presence of human activity in the Azores Islands long before the arrival of the Portuguese navigators of the XVth century, there is no clear evidence which enables us to identify which specific culture may have existed in the Azores before the Portuguese arrival.