Altenau ( ) is a town and a former municipality in the district of Goslar, in Lower Saxony, Germany. Since 1 January 2015 it is part of the town Clausthal-Zellerfeld.

Clausthal-Zellerfeld is a town in Lower Saxony, Germany. It is located in the southwestern part of the Harz mountains. Its population is approximately 15,000. The town hosts the Clausthal University of Technology. The health resort is located in the Upper Harz at an altitude between 390 and 821 m above sea level.