Global city populations are visualized as semi-transparent points on a natural Earth projection, with point size encoding population via a square-root scale and a maximum radius of 15 pixels. The map includes graticules, country borders, and landmasses rendered using `d3.geoPath` and world-atlas TopoJSON data. City coordinates and populations come from a CSV loaded with `d3.csv`, while the React application uses hooks to fetch and render the visualization with SVG.