Wonder Tales from Many Lands by Katharine Pyle

The Prince wondered greatly at his father’s words, but he took the key and went to the top of the castle, and there he found the steel door his father had described. He unlocked it with the silver key, stepped inside, and looked about him. When he had done so, he was filled with amazement at what he saw. The room had twelve sides, and on eleven of these sides were pictures of eleven princesses more beautiful than any the Prince had ever seen in all his life before. Moreover, these pictures were as though they were alive. When the Prince looked at them, they moved and smiled and blushed and beckoned to him. He went from one to the other, and they were so beautiful that each one he looked upon seemed lovelier than the last. But lovely though they were, there was not one of them whom the Prince wished to have for a wife.