The River Holtemme flows through the town and, not far from its western gate, it is joined by the Zillierbach stream, which is also known as the Flutrenne near its mouth. North of the town the Barrenbach flows through several ponds and empties into the Holtemme in the village of Minsleben. The historic town centre consists of an old town and a new town (Altstadt and Neustadt). The town's borough includes Hasserode, Nöschenrode, the residential estates of Stadtfeld, Burgbreite and Harzblick as well as the villages of Benzingerode, Minsleben, Silstedt, Schierke and Reddeber.

The borough measures 9.5 km from west to east and 6 km from north to south. Its highest point is the Brocken, at 1,141 metres above NN, and its lowest is at 215 metres.

The town lies on the German-Dutch holiday road known as the Orange Route.

The Northern Harz Boundary Fault crosses the borough along which the watershed between the Weser and Elbe runs. To the north precipitation flows into the Weser, to the southeast, later northeast, waters flow into the Elbe. This fault line runs through the quarter of Hasserode. It can be made out in the east of the town at the Schloßberg.

The North Harz Fault cuts through the borough along which the watershed between Weser and Elbe rivers runs. To the north of the fault line, the precipitation flows into the Weser; to the southeast, later northeast, waters flow into the Elbe. This fault runs through the suburb of Hasserode. To the east it is manifested in the town's castle hill.