Buy a 16 or 18euro three day ticket on the local steam train network(not shown on website!) And use it to visit many of the below ideas
HSB
Walk part of the pilgrims road to Santiago de Compostela
Pilgrims road
Water fall five minutes walk around the corner
Waterfall around the corner
Visit Gernrode Cathedral and see how Canterbury Cathedral would have looked before it was burnt down in 1067!
stiftskirche-gernrode
Swim with the fish in a forest Lake
Swimming lake
Climb Harz's 'Eiffel Tower', the largest double cross in Europe
Josephskreuz (Joseph's Cross)
Go a bit futher and visit the massive and only Anhydrite show cave in Europe
Barbarossa Cave
And of course choose a castle
Falkenstein Castle- in the same valley as us
Ballenstedt Palace
Harzgerode Castle
Quedlinburg Castle