A radial tree diagram displays a hierarchical classification of countries by world region and subregion, sourced from a JSON file named `countryHierarchy.json`. The visualization shows the World as the root, branching into continents like Asia, then subregions such as Southern Asia, and finally individual countries. Built with D3.js v4, the code uses `d3.cluster` to compute the tree layout and `d3.hierarchy` to process the data. Nodes and connecting links are rendered as SVG elements, while `d3.zoom` enables panning and scaling. Text labels are positioned radially, with rotation adjusted based on each node's angle.