This episode is a time travel to the Celtic era, to examine historical mysteries and discover more about Celtic culture. I will tell you about the druids: what we know of their emergence, their functions, their cultural importance, and also the many aspects of druidism that remain mysterious. We will also travel to the Hill of Tara in Ireland, examine the mystery of the vitrification of hillforts, and take a look at the enigmatic Gundestrup Cauldron.