Throughout history people have fought each other. So people used to make their towns and villages safer by building fences or ditches around them. Starting in about 850, during the medieval period, people in Europe built castles, or defended homes just for a lord and his household. The lord, his family, and his servants and soldiers all lived there. All the land and castles belonged to the king, but the lord could live in the castle as long as he was loyal to the king.