Cusco, in the Peruvian Andes at 3,400m, sits under thin, clear high-altitude air with quick access to some of the darkest skies in South America. The Bortle 6 city glow gives way to Bortle 2–3 skies in the surrounding Sacred Valley and high Andes. At 13.5°S, the galactic core passes nearly overhead, and the southern Milky Way is spectacular. Andean astronomy has deep roots — the Inca read dark-cloud constellations in the bright band of the Milky Way, structures visible only under genuinely dark skies. The dry season (May to October) offers the clearest, most reliable nights.