The amphitheatre

First stop to observe the “stones”. Strata are visible, so we have a sedimentary rock. 300 million years ago a chain of mountains covered what was to become France. Eroded, it left space for a warm, shallow sea. At the bottom of this sea, the sediments were deposited and our rock began to form between -240 and -233 million years. In 7 million years a rock thickness of about 150 m was created. We can only see about 5 metres here. It is grey limestone. The uplift of the Alps 80 million years ago moved and carried this rock to where we walk today.