After a decade of research the functions of circular enclosures of the middle Neolithic are still debated. In a project funded by the German Research Foundation (DFG) two of these roundels were excavated in order to learn more about their structure, history of construction, their function as well as their spatial characteristics. Based on high-resolution digital elevation models, possible orientations towards topographical and astronomical features are systematically investigated using a GIS-based visibility analysis and a self-developed tool in Wolfram Mathematica. In this article preliminary results of two (partially) excavated roundels in the northern Forelands of the Harz Mountains are presented.