A building structure on the summit of the Umm al-Biyara in the ancient Nabataean capital Petra in Jordan was identified as a possible Nabataean watchtower due its prominent strategic position on the hilltop. In this article, GIS (Geographic Information System)-based viewshed analyses investigate the interpretation of the structure as a watchtower and assesses the intervisibility to other presumed towers in the area. The aim of this paper is to present a preliminary model for reconstructing the Nabataean communication and defense system of the Petra hinterland. In order to define a better classification of the visible areas derived from the GIS-calculations, the so called Higuchi-viewshed analysis was applied, which classifies the range of visibility to calculated distance values. Since research on the spatial organization of the ancient city of Petra is limited, this paper will not only evaluate the above mentioned analysis method critically, but will also discuss further steps in investigating the Nabataean defense system.