who were the first stone castle builders in medieval europe?

The First Medieval Stone Castle Builders in Europe were 8th-c Muslims, Not Normans or Carolingians!

Stone fortresses with curtain walls, keeps, gatehouses and postern gates have existed in Europe for thousands of years before the Middle Ages. For instance, Mycenae on Crete (1350 BC) has all the characteristics of a medieval castle. Despite this, many scholars agree that the Normans were the ones to popularize castles in Europe, let alone medieval Europe. After all, the British Isles did not see many castles being built of stone until after the Norman Conquest of 1066…