A world map displays cities with populations over 50,000 as semi-transparent teal circles sized by population using a square-root scale. The map renders via SVG with a natural Earth projection from d3.geoNaturalEarth1, with country boundaries, land masses, and graticules drawn using d3.geoPath. React manages the component state, fetching city data from a CSV via d3.csv and world topology from TopoJSON using d3.json, with the feature and mesh APIs extracting land and interior boundaries.