This example presents a world map with cities sized proportionally to their population, using a square-root scale to encode the data. The visualization renders geographic features like landmasses, graticules, and country boundaries using `geoNaturalEarth1` and `geoPath`, while city points are drawn as SVG circles positioned via the projection. The map is built with React and D3 v5, pulling city data from a CSV of the Simplemaps World Cities Database and country topology from World Atlas TopoJSON.