I read this book in the late 1990s. It’s a picture book, with detailed illustrations. I remember rich colors, and I think they looked like watercolor paintings. What I remember of the plot: there are two princesses (maybe they’re cousins), and one lives in a castle or palace of crystal or glass. The other princess comes to visit her in her glass/crystal palace, and she arrives by boat—I think the illustrations are of a city similar to Venice, where the streets are canals, and I remember fun bridges with lots of stairs. I was intrigued by the details of the buildings in the drawings. Part of the story may have been that the princess who comes to visit lives in a palace made of some other specific material—brick, stone, wood—something like that, but I’m not certain. And she decides that she would rather go back to her palace of glass.