View of the Alpha/alpha barrel architecture (CATH classification 1.50) on the CATH website. The Classification Lineage shows the selected architecture is placed in the CATH hierarchy, and the Summary of Child Nodes gives the number of nodes further down. The selected architecture comprises two topologies, 1.50.10 and 1.50.30, shown in the Summary pane below. Direct links to the CATH pages corresponding to the topologies, as well as links to representative domains, are available alongside the topology names. By clicking a link to a representative domain, an output as in Figure 1 is obtained. Navigation on all levels of the CATH hierarchy is facilitated by an analogous page layout.