Several tools have been proposed to automatically create thematic maps. A common drawback of these tools is that they rarely provide means for users to explore their decision trees. Users may thus create maps or get some maps proposed, but not know why some suggestions of maps were made. To address this gap, this work introduces 3D4DT, an approach to explore decision trees as a three-dimensional interactive scene. The 3D4DT approach uses JSON as a machine-readable format to represent decision trees and maps JSON elements to user interface elements (e.g. radio buttons and cubes). A preliminary evaluation of 3D4DT has shown effectiveness gains in comparison to information displayed as text+picture, for a decision tree with a simple hierarchical structure. The contributions of this work are relevant to the design of more transparent software for automated thematic map creation.