We present the H3 layout technique for drawing large directed graphs as node-link diagrams in 3D hyperbolic space. We can lay out much larger structures than can be handled using traditional techniques for drawing general graphs because we assume a hierarchical nature of the data. We impose a hierarchy on the graph by using domain-specific knowledge to findan appropriate spanningtree. Links which are not part of the spanning tree do not influence the layout but can be selectively drawn by user request. Thevolume of hyperbolic 3-spaceincreasesexponentially, as opposed to the familiar geometric increase of euclidean 3-space. We exploitthis exponential amountof room by computingthe layout according to the hyperbolic metric. We optimize the cone tree layout algorithm for 3D hyperbolic space by placing children on a hemisphere around the cone mouth instead of on its perimeter. Hyperbolic navigation affords a Focus+Contextview of the structure with minimal visual clutter. We have successful...