Using visualization and exploration tools can be of great use for the understanding of a software system when only its source code is available. However, understanding a large software system by visualizing only its lower level artifacts (e.g., classes, methods) and the relations between them does not scale for industrial-size systems. To address the scalability issue, higher level hierarchical abstractions (e.g., package structure, clustered decompositions of the system) should be used together with relations between them that are usually aggregated from the lower level relations. In this paper, we present the concepts behind Softwarenaut, a tool aimed at exploring any kind of hierarchical decompositions of a system, and then we look at a specific exploration of a system. In the experiment, the hierarchical decomposition of the system is the result of applying a semantical clustering to group classes that use similar terms.