This example visualizes the populations of cities on a world map, using circles sized proportionally to population data. It shows a geographic context with landmasses, graticules, and sphere outlines, layered with semi-transparent teal points. Built with React and d3.v5, the map uses `geoNaturalEarth1` for projection and `geoPath` for rendering. City data is loaded from a CSV, while geographic boundaries come from the world-atlas TopoJSON dataset. Circle radii are scaled using `scaleSqrt`.