This example visualizes cities with populations over 50,000 as semi-transparent circles on a natural Earth projection. The map displays country boundaries, interiors, graticules, and a sphere outline, with circle size scaled by population using `d3.scaleSqrt`. The React-based visualization uses `d3.geoPath` for geographic rendering and `d3.geoNaturalEarth1` for projection, with city data loaded from Simplemaps via CSV and country shapes from World Atlas TopoJSON.