The Katastralgemeinde Unterdöbling lies in Döbling, the 19th district of Vienna, to the north of Oberdöbling. The border between Unterdöbling and Oberdöbling is largely determined by the Krottenbach, a stream which today serves as a canal. The medieval town centre lay in a dip by the stream, where nowadays the Rudolfinergasse and the Nußwaldgasse (which used to be called the Herrengasse) lie. In more recent times, settlement took place on the plateau that rises slowly to the west and to the north towards the Kahlenberg. Unterdöbling's southern border runs alongside Oberdöbling, in the west it borders on Untersievering and in the north on Grinzing as well as on parts of Heiligenstadt. The eastern border is marked by a road leading from Oberdöbling via the Hohe Warte to Heiligenstadt.