This example displays a world map with circles sized proportionally to city populations, using data from the Simplemaps World Cities Database. The map renders geographic features with d3.geoNaturalEarth1, d3.geoPath, and d3.geoGraticule, while country boundaries load from World Atlas TopoJSON. City points are placed via projection coordinates and scaled with d3.scaleSqrt, all built within a React component using SVG. The visualization includes graticules and styled land, sphere, and interior paths for a polished cartographic look.