Druids, what were they?

Existing from ancient Gaul, modern spain, and Portugal, to Ireland, Scotland, and the rest of the UK. Much of what we know come from there destroyers, Ceaser and roman historians, a few more reliable texts from Greece. Modern wiccans seem to have placed some claim to them, when we see they were so much more. They were doctors, judges, story tellers, and among other things priests. Many spoke Greek, and were educated in astronomy, herbology, and the natural sciences. Looking at some of thier artifacts people were confused trying to understand what these odd metal devices were. Then a doctor noticed many of the tools could be exchanged for the tools in any modern surgery, so like ancient Egyptians and mayans they were adept at biology and surgery. On a semi-related subject, the frozen ice-man had blue tattoos of dots in strange places, they found those exact spots where acupuncture spots, for medical problems, which the iceman suffered from based on x-rays, and MRI's. Where did all this advanced knowledge come from? Just something to think about.