This example presents a world map with circles sized proportionally to city populations, using an equirectangular projection. The visualization layers country landmasses, interior boundaries, and graticules from World Atlas TopoJSON data, with city positions plotted from latitude and longitude coordinates. The code uses d3.geoPath for map rendering, d3.scaleSqrt for circle sizing, and React hooks to load CSV city data and TopoJSON topology. All marks render as SVG elements within a React component structure, with styling applied through CSS classes.