This was a review that got me thinking but in the end I decided on three stars. Read below why. If you continue please keep one thing in mind. There was nothing especially wrong with this hotel, just that it was imo not a 5 star experience.
The hotel is nicely situated on a small lake in the middle of the villlage of Ilsenburg, so you have nice views of the Harz and a lot of attractive landscape nearby. Also the towns of Wernigerode and Vienenburg are just tow short hops with a car away (10 and 25 min respectively).
The room (lowest category) was a bit small due to the geometry of the building, so in fact a triangle was cut off. It does offer a very nice bed, some seating opportunities and enough space, yet the TV is a very small one and if you open the minisafe literally no one can use the WC. Also some hard edges in the floor stuck out. The bathroom is very nice, clean and bright with a very good shower and a large sink but on the other hand the towels are quite thin and it does not offer individually bottled amenities.
You can get a ride form the trainstation for free which was even possible with a couple of minutes notice and the staff at the reception was very helpful and friendly througout the whole stay.
Breakfast does offer good choice of cheese, fruit, cold cuts and some hot dishes but it surely lacks in the berad department. Germany is THE country for bread and having only 2 sorts of rolls and 2 of bread does not do justice to this. The setting is very good, nice view of the lake and the Hartz, the service could improve a bit.
The spa itself is nice at least the pool area, all you can expect from an indoor pool area in a hotel. The Saunaarea well, it contained one small sauna (4 people and it felt cramped) and only 5 opportunities to lie down of which 2 were directly adjacent to the water station and the door to the outside Sauna. So too small in all.
We did book an arrangement with two set meals in the restaurant and both of the meals were ok but nothing too spectacular. One day we had a wonderful waitress being very kind and nice (Dankeschön, Bitteschön) which made up for a lot, but the other evening the waitress was unable to keep our glasses topped, our request for the wine list for a dessert wine was answered with bringing a dessert wine directly... it was far from seamless. The winelist is pretty short and way overpriced.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC.