Who says "pebbles" said "river"

Towards the top of the hill, the rollers become increasingly abundant. They are in shape, size and colors and sign the existence of an ancient river. For one roller is a piece of rock torn from the mountains by erosion and transported to the bottom of a river or sea, using and is slowly rounding. The rollers of Ansouis have very different origins, and sometimes far as the Alps, brought to this place by a paleo-Durance flowing out there 8 million years.