Paradiso is the Italian word for "Heaven." It also happens to be the setting for the book. Now the origins of the English Italian word "paradise" are interesting. The English word comes from the Old French. Both French and Italian words comes from the Latin. And as is often the case, the Latin word comes from the Greek word meaning "park," "garden," or "pleasure-grounds." Without getting too distracted by the "pleasure-grounds" part of that, we'd like to bring your attention to the second word there: garden. This makes us think of that most famous garden of them all: the Garden of Eden.
So Heaven is supposed to be modeled after the earthly Garden of Eden. Or rather vice versa, since Heaven was created first. The point is that Heaven, like a well-tended garden, is beautiful and organized. Why? Because gardens aren't just some random offshoot of nature. They are created. They have a creator. In the case of regular gardens, the makers are men. In the case of Heaven, the creator is God. He is the one who ensures that everything is in its proper place. All those different spheres in Paradiso separated by atmospheres, inhabited by only the worthy, all ultimately surrounded by the Empyrean (the tenth and final Heaven), all show the work of an artist, God.