This example shows the autonomous regions of Spain displayed as a preprojected TopoJSON topology. The map is rendered using the `d3.geoPath` function to draw the polygon and MultiPolygon geometries, with shared arcs efficiently referenced between regions to form the composite border. The code loads the TopoJSON file with a `transform` and `scale` property, indicating the data is preprojected into planar coordinates. The visualization uses the D3.js library to parse and render the topology, demonstrating how complex boundary data can be compactly encoded and reproduced without a full geographic projection system.