This example displays a world map with circles sized proportionally to city populations, using a square root scale to encode population values. The visualization renders geographic landmasses, graticules, and interiors via D3’s `geoNaturalEarth1` projection and `geoPath`, while city points are positioned with the same projection. Data comes from a Simplemaps CSV of cities with populations over 50,000, and country boundaries from TopoJSON’s world-atlas. React manages the component state, and SVG circles use a max radius of 15 pixels with a teal fill.