Italo Calvino's book Invisible Cities is essentially a collection of descriptions of cities.
What I find interesting is that the chapters follow a specific structure. There are ten categories of cities, labeled "Cities & Memory", "Cities & Desire", and so on. The book is also divided into ten chapters. It's hard to describe the structure, but here's wikipedia's description:
The matrix of eleven column themes and fifty-five subchapters (ten rows in chapters 1 and 9, five in all others) shows some interesting properties. Each column has five entries, rows only one, so there are fifty-five cities in all. The matrix of cities has a central element (Baucis). The pattern of cities is symmetric with respect to inversion about that center. Equivalently, it is symmetric against 180 degree rotations about Baucis. Inner chapters (2-8 inclusive) have diagonal cascades of five cities (e.g. Maurila through Euphemia in chapter 2). These five-city cascades are displaced by one theme column to the right as one proceeds to the next chapter. In order that the cascade sequence terminates (the book of cities is not infinite!) Calvino, in chapter 9, truncates the diagonal cascades in steps: Laudomia through Raissa is a cascade of four cities, followed by cascades of three, two, and one, necessitating ten cities in the final chapter. The same pattern is used in reverse in chapter 1 as the diagonal cascade of cities is born
Wikipedia also provides a helpful table that allows you to "see" the structure visually.
My question is: how does this structure contribute to the meaning of the book? In other words, why did Calvino spend so much time creating this structure?