This example displays a natural Earth projection world map with graticule lines, country borders, and interior boundaries. City populations are plotted as semitransparent circles with radii scaled by the square root of population using `d3.scaleSqrt`. The visualization uses React hooks to load world atlas TopoJSON data and a CSV of global cities, converting them into GeoJSON features via `topojson.feature` and `topojson.mesh`. D3’s `geoNaturalEarth1` projection and `geoPath` render the SVG shapes.