World's largest known display of open air paleolithic rock art

Before seeing the signs as we drove into town, we'd never heard of "Vila Nova de Foz Coa", a village in the upper Doura Valley (NE Portugal); nor did we know that the region has the largest known display of open-air (ie not cave) Palaeolithic rock art in the world.  It is World Heritage Listed. The rock art is only visible on guided tours taken from the Museum of the Parque Arqueologico do Vale do Coa on the outskirts of the village. 

The rock engravings were discovered during a proposed hydro-electric dam environmental impact assessment in the early 1990s. Several thousand rock engravings are etched for 17km along the Coa and tributary valleys. The engravings include thousands of images of four tyes of animals: horses, aurochs (wild extinct ancestor of modern cattle), long horned ibex (wild goat), deer. The images have been dated from 40,000 to 10,000 years ago.

The prehistoric engravings are made using three techniques, they are scratched, picked or gouged. Sometimes a combination of these techniques are used. The vertical schist slabs are used as a canvas. 
The schist rocks along the northern part of the Coa River mouth contain large drawings in contrast with smaller depictions in other parts of the region. Their size varies between 15cm and 180cm, but most are 40–50cm. The style often features bold lines, but many are touched with fine, thin lines.
Generally, these images are stratified, with new designs drawn over the pre-existing carvings. This makes it difficult to distinguish each of the animals. Our guide Luiz showed drawings of each carving separated form the others then traced the carving with the tip of a stick to help us clearly see the image. The day of our tour way foggy and rainy making it difficult to photograph the images.    

We learned from Luiz that sometimes there were many thousands of years between layers of etching. His theory is that each animal represented a totems of a tribe. 
The importance of this prehistoric art site remains its rareness and extension. 
Tanya has managed and written many impact assessments in her career. It was exciting to see (again) first-hand the relevance and significant value such a process brings. Without it, the world would have lost this rich historical art.