A map of Estonian counties rendered as an SVG using React and D3. The visualization uses a Mercator projection via `d3.geoMercator` and `d3.geoPath` with `fitExtent` to scale the map to the viewport. County boundaries are drawn as brown filled paths with darker stroke outlines, while interior borders are highlighted using a TopoJSON mesh. The geographic data is loaded from a remote TopoJSON file and processed with `feature` and `mesh` from the topojson library.