Schloss Herzberg is a jewel of half-timbered architecture.
The complex has remained in Braunschweig ownership for over 700 years since Heinrich dem Löwen, who exchanged the former imperial castle of Barbarossa for Swabian possessions.
The present building, dating from 1510, was for a long time the residence of the Grubenhagen line of the House of Brunswick-Lüneburg. It was Duke Georg (1582-1641), who left Herzberg in 1636, made Hannover his residence. His descendant, Georg I (1660-1727), was made King of England.
There is also a museum in the Welfenschloss in Herzberg. One section of the museum presents the history of the Guelphs in Herzberg, including a facsimile of the Gospel of Heinrich dem Löwen. In the museum the focus is on Schloss Herzberg as a residence. The museum also shows special aspects of the town and economic history: the Herzberger Gewehrmanufaktur (gun manufactory), mills in Herzberg and the organ builder Johann Andreas Engelhardt, who had his workshop in Herzberg. As a special feature, the museum has a playable functional model with original components from historical Engelhardt organs, which are used regularly for organ concerts. All departments offer activity stations, for both children and adults. The museum also houses an exhibition by the Landesforstverwaltung Niedersächsischen (Lower Saxony State Forestry Administration) on the forest history of the Harz Mountains and on the connections between forest use, forestry and ore mining, as well as a presentation by the Esperanto Society Südharz e.V.