I'll have to read up on literary tropes as I'm having a hard time picking out which ones are being explored in some of the stories. For example, the city of "Armilla" is described as being nothing but a series of pipes topped with sinks, toilets, bathtubs, etc. To me, Marco Pollo (and Calvino) are forcing the reader to think of a mostly invisible system that is a _huge_ component of any city: plumbing.
There is a fairly strong argument to be made that the entire book is just a love letter to Venice. From the wikipedia:
In one key exchange in the middle of the book, Kublai prods Polo to tell him of the one city he has never mentioned directly—his hometown. Polo's response: "Every time I describe a city I am saying something about Venice."
I don't think that Invisible Cities usefully reduces down to "talking about a specific city". It talks all about cities, how people live in them, see them from the outside, etc. To say that it's just "all about Venice"—like the back of the book does—flattens the book in a way that takes away everything interesting about it.
Or maybe better put: it's clearly not literally all about Venice, since the cities as described do not (and can not) exist. So why make it figuratively all about Venice?
This reminds me that there is reference to "Armilla" also in Kundera's "Unbearable Lightness of Being": Even though the sewer pipelines reach far into our houses with their tentacles, they are carefully hidden from view, and we are happily ignorant of the invisible Venice of shit underlying our bathrooms, bedrooms, dance halls, and parliaments.
