Cities of the World uses a natural Earth projection to display global population data as proportional circles. D3’s geoNaturalEarth1 and geoPath render landmasses, graticules, and sphere outlines, while a sqrt scale maps city populations to circle radii. The visualization loads world atlas topology from world-atlas and city CSV data, overlaying semi-transparent dots atop a muted map. React manages the SVG rendering, with d3.v5 providing the underlying geospatial and scaling utilities.