A hierarchical tree visualization displays world countries organized by continent and subregion. The data structure nests nations under regional groupings like Southern Asia and Western Asia. Using D3 v5's `d3.tree` layout and `d3.hierarchy`, the example renders SVG paths with rounded corners via a custom link generator. Text labels use a Playfair Display font, with font size scaling by node depth. Users can pan and zoom the entire visualization through D3's `d3.zoom` behavior.