Information visualizations have become popular tools for extracting knowledge from large bodies of information. Very little is known on the usability of such ‘visual knowledge tools’ for information access. The goal of this paper is to show the usability of the spatial metaphor ‘scale’ to access a large semantic document space. An experiment was conducted to examine whether different user groups can associate graphical changes in resolution in spatialized views with changes of level of detail in an index hierarchy of a digital document collection. Test participants were asked to utilize zoom tools to explore a spatialized subset of the GeoRef database, an extensive collection of geology and earth sciences documents. The outcomes of the experiment suggest that people are able to associate graphical changes in resolution of spatialized views (zooms) with changes in levels of detail of a document collection (hierarchical order). These results are independent of user group membership, but for some displays it takes people longer to make a decision.