One of the side affects of a Dam Project along the Coa River in Portugal was the survey and discovery of an extensive network of pre-historic rock art which dates from 22,000 years ago to the present in several historical layers. The earliest paintings are from 22,000-20,000 years. The second set of drawings date from 16-10,000 years and is more plentiful. Further art works are seen throughout human existence from the Epipaleolithic period, the Neolithic, the Chalcolithic and Bronze Ages, into the 5th and 1st centuries and finally the 17th to 20th century which includes trains.plane and bridges alone with religious and anthropomorphic and zoomorphic designs that included weapons and symbols, an extrodanory cocktail of human prehistory to history.