A world map visualization displays global cities as semi-transparent circles, with the circle size proportionally representing each city's population, layered over a graticule and world atlas landmasses. The example uses React to render SVG paths for the sphere, graticules, and land features, while city markers are positioned via the `geoMercator` projection. Population data from the Data Canvas Sense Your City Dataset is mapped to radius using `d3.scaleSqrt`, with the `d3.geoPath` and `d3.geoGraticule` APIs handling geographic geometry.