The plugin provides functionality to organize spaces hierarchically in spaces and sub-spaces. It includes macros to display the space hierarchy on the dashboard or in navigation menus. The relationship between the spaces is rather lose (e.g. no permissions or layouts will be inherited), since the plugins focus is on structuring a wiki and its spaces.
Structure spaces hierarchically
Space navigation bar on every page
Also supports external links which are hierarchable as well
Dashboard module to show space structure
Subspace quicksearch macro to search inside current space and it's subspaces