There is a legend connected with the history of the construction of Frankenberg Castle. During the wedding of Charles and Fastrada there was a snake in the hall holding a ring in its mouth. The snake threw the ring into the cup filled with wine, Charles took it out and put on the bride's finger. Allegedly, the secret of the love that Charles had for his wife is in this. When Fastrada died, Charles plunged into depression. The court arranged a hunt to entertain the monarch. During the hunt, Charles dropped his wife's wedding ring he was carrying with him. It was decided to build a castle at the place, where the king dropped the ring. Its name translates as "Mountain of the Franks."
There is another legend associated with Frankenberg Castle. It is believed that this story prompted Tolkien to write the saga "The Lord of the Rings." After the death of Charles the castle passed from hand to hand. It got its present look in the XIV century. The then owners from the Flemish House of Merode-Houffalize rebuilt it. No one has lived in the castle since the XVIII century and it was gradually destroyed. But in 1834, the city fathers decided to restore Frankenberg. Now its walls house Aachen’s Museum of History and the local cultural center.