Ulfberth sword found in Finland. Smelting technology that wont be repeated by any other culture for centuries. The Vikings were among the fiercest warriors of all time. The feared Ulfberht sword. Fashioned using smelting techniques that would remain unknown to the Vikings' rivals for centuries, the Ulfberht was a revolutionary high-tech tool as well as a work of art. Considered one of the greatest swords ever made.