Location from remembrance-of-earths-past by
The barred-spiral galaxy that contains both the Solar System and Trisolaris — and, somewhere unseen in its depths, the Singer who throws photoids and the Abyss-Gazers who fold civilizations into two-dimensional smears.
The Milky Way is the trilogy's true setting. Earth is local. Trisolaris is local. The civilizations that throw the dual-vector foils and the photoids are everywhere and nowhere, with practical anonymity over four-light-year distances. The galaxy is the explanation for why everyone is afraid: the speed of light is just slow enough that you cannot afford to assume your neighbors are friendly.
From outside, an ordinary barred-spiral galaxy 100,000 light-years across, two major arms and several spurs, a massive black hole at the core. From inside, an arch of milky light across a clear night sky on Earth, indistinguishable from beauty. From the trilogy's later perspective: a forest with hunters in every tree.