A radial tree displays a hierarchy of world countries, organized by continent and subregion, radiating outward from a central root node. The visualization uses an SVG rendering with D3 v4’s `d3.cluster` layout to position nodes, and custom bezier paths for links. Text labels are rotated and sized by depth, with a heavy white glow for readability. Panning and zooming are implemented via `d3.zoom`, while the JSON data structure defines the nested country groupings.