I booked this hotel for 9 days. Moved to another one after 2 days.
Tiny rooms are crying for renovation.
Gym is a joke: three machines on 15 sq. meters, one of which is not working, another one is about to stop working.
Internet, which is a must-have for a 4* hotel, costs per day about as much as what I pay per month - 17 Euro, yet I haven't managed to connect (even with a cable).
Staff - some are friendly, some are not. Two of the three people I had to deal with at the reception were nice and helpful, the third guy was very arrogant.
Rooms might be cleaned daily, but that you will hardly tell, since the carpets on the floor are worn out, should have been changed years ago. The same applies to a tiny bathroom.
I booked a non-smoker room, but I had smoke from my neighbors through ventilation.
I will give the hotel 2 points: one - for very good breakfasts, another one - for convenient location. But that's about it.

One of the older hotels. Elevator has the same age as the hotel.

Four star may be somewhat exaggerated and price is not cheap, but still, this is the best hotel I have found in Karlsruhe since Kaiserhof, which was my favorite, closed.

Restaurant is not bad. But again, not cheap either.

Whenever one enters a hotel room for the first time there are clues to the underlying character and likely comfort of the overall experience. Is there a bowl of fruit, perhaps? Or a selection of pillows, ranging from hard to soft? Or fluffy, towelling bathrobes? Well, the Schloss gives a hint – just a hint - of what you may experience by placing earplugs neatly by the bed.

The benefit of this hotel for the tired traveller is that it is a couple of hundred metres from the station, so a short walk and you are in the warmth and comfort of what is actually quite a nice hotel. The antique elevator is fun, and creaks more each time it is used; in the reception and bar the overall ambience is to be enjoyed, and the restaurant is really rather good and should not be overlooked. The gym and sauna are also OK, but in three days I never actually found a light switch for the gym so enjoyed working out in the dark. But underlying these positives is the simple fact that the hotel stands next to the railway.

So if you are somewhat hard of hearing, need somewhere near the station, need to be awake early, or have tried all of the other generally mediocre hotels in Karlsruhe and need a change, then the Schloss is for you. If you are a light sleeper, then it is probably best avoided.

We staged a business conference at this hotel. The bedroom was very comfortable with window overlooking the park/zoo opposite. The hotel is across the road to the railway station which was very convenient, especially when I was carrying quite a bit of materials for the conference. The hotel itself has a lot of history and I used their lift installed in 1914! We had the conference in the big study with books and bookshelves giving an ideal, and unusual surrounding.