Starting from two beautiful beaches in NW Chios, Agia Markella and Lampsa, we head towards the asbestos mines in Keramos and the thermal baths of Agiasmata. This geotrail passes through the oldest rocks of Chios, which unfold their history of the distant geological past and "speak" of the lost ocean of Paleotethys. They constitute a unique destination in the world, as these rocks – formed in a previous orogenic cycle, the Variscian or Hercynian orogeny, and some of them are 420 million years old – have preserved characteristics that help geoscientists understand the processes of the earth during that period and the paleoenvironment.