La Paz sits at around 3,640m in the Bolivian Andes — the highest capital city in the world — giving it some of the thinnest, clearest air over any major city. Above much of the atmosphere's haze and water vapour, transparency is exceptional. The Bortle 7 city glow gives way quickly to dark Altiplano skies, and the high plateau and nearby salt flats reach Bortle 2 with pristine conditions. At 16.5°S, the galactic core passes high overhead, and the Magellanic Clouds and southern Milky Way are stunning. The dry season (May to October) offers the clearest, most reliable nights.