Ludwig II, Landgrave of Thuringia, nicknamed Louis the Iron (1128 – 14 October 1172 at Neuenburg Castle in Freyburg).

The relationship was so good that it was arranged that Louis II should marry Judith, who was a niece of Conrad III and a half-sister of his successor Frederick Barbarossa.

Until Conrad's death, Louis II stayed at the royal court, where he was given an education by the archbishop of Mainz and the bishop of Merseburg.

According to a legend, which was recorded by Johannes Rothe in 1421, Louis II was travelling anonymously and one night, he found shelter with a blacksmith in Ruhla.

The palace was constructed in its present form — radiocarbon dating shows that the oaks for the roof beams were felled in 1157.