This interactive visualization combines a world map with a time-series bar chart to explore urban building density data. Users brush over the date histogram to filter cities on the map, with circles sized by total building counts via d3.scaleSqrt. The map uses d3.geoNaturalEarth1 and d3.geoPath to render land masses and graticules from World Atlas TopoJSON. React’s useMemo optimizes rendering, while d3.brushX links the two views for fast, responsive filtering.