Grätzlhotel Belvedere in Vienna

This was by far the worst hotel experience I have ever had. The only positive aspect of this place is its location.
On the first day of our arrival in Vienna, we were unable to find the hotel despite using the address provided. The confirmation letter stated that the room was located at Theresianumgasse 35, yet there was no visible number 35 on the building — it appeared to have been removed. We found the place purely by chance. No reasonable guest would expect a hotel room to be located there.
When we finally discovered the entrance, we were shocked to see that it was nothing more than an aluminum door opening directly onto the street, with no reception area, no secondary entrance, and no security. This immediately made us feel unsafe for the entire duration of our stay.
On the very first day, we experienced serious problems with hot water in the shower. In the mornings, there was no hot water at all. When we reported this issue, the staff openly admitted that there was a problem with the hot water system and stated that they were unable to fix it at that time. We requested to be moved to another room in the same location, but instead we were offered a room at a completely different property, far away from the city center, which was unacceptable for us. As a result, the hot water problem was never properly resolved.
Additionally, housekeeping service was completely inadequate. The room was not cleaned unless we repeatedly complained. We were told it would be cleaned on the third day, but it was not. Only after complaining again was the room finally cleaned on the fourth day — the last day of our stay — making the cleaning service essentially useless.
Due to the lack of basic safety, poor communication, unresolved hot water issues, and extremely poor housekeeping, we strongly advise against staying at this place. This accommodation does not meet even the minimum standards expected from a hotel.

Firstly, the key safe code system was not working, I had to ring the office to get a key down to me and got snapped at by the call responder when stated I had been waiting in the cold for a while and the code wasn’t working.
My first night was extremely cold, the heating wasn’t working, I sent an email the next morning to complain about this and instead of getting a response to advise me of the solution, they didn’t respond, they just sent a man to my room, I was in the shower when he arrived and didn’t hear he was knocking, next thing I knew he was getting into the room and I had to fly out of the shower, grabbed a robe and shouted to stop him from coming in. What I expected was for the office to obviously inform me that they were sending someone to check the heating out. As if that wasn’t enough, few minutes after that happened, I had 2 men also try to get in the room, when I asked what they wanted, I was told they were there to check that the fire hydrant is safe for me. Why wasn’t the fire hydrant tested before I checked in. As a frequent female solo traveller this is the first place I stayed that I felt this unsafe. I was anxious the rest of my stay there, luckily no one else turned up but the first two times left me with anxiety. They need to learn to properly communicate with the occupants that’s the whole point of getting our contact information isn’t it.

At the last moment they informed us that the flat I had booked for my daughter since many months ago, for the Xmas holiday, is no longer part of their offer.
What shall I say!!
It's unacceptable and makes us feel miserable.

Falsely advertises AC, see image. I'm sure this would be a nice place to stay in the winter, but it is summertime here and the room is 83° f / 28° c. No windows to open for ventilation. This is unacceptable. They do provide a fan, but it's a Band-Aid. I will be asking for a refund.

Edit. I was going to revise this review, however the owner confronted me the next morning and gave me a sob story about how the Google algorithm is to blame for bad information. If you care so much about your Google reviews then say on top of your Google maps information. Also, you pride yourself in being an architect and small business owner, then design in some AC and own up to this issue. I see reviews from years ago about this problem. Yes, I booked through your website via Google Maps. Like you say, it says nowhere about having AC or lacking it. Perhaps you should make this clearer if you want better ratings. Also I did call last night and was told 1) there is AC (false), 2) It was too late to transfer rooms, and 3) that it was not possible to issue a refund and that no promises could be made the next morning. If I could give below 1 star I would. Stay away.