I travel to Mannheim at least 3 times per year and have a favorite hotel and a number of runner's up that are good, but not quite as good as my favorite. When I first started this job 7 years ago, I tried the Dorint, because it is a "name" hotel. I hated it then - it's still terrible now.
A colleague accompanied me to a trip to Ludwigshaven (just across the river), and her secretary picked the Dorint for us. Since I hadn't been there in 7 years, and she was convinced it was a good choice, I said nothing. Also, I had heard that it had been renovated in the meantime - could it still be as bad as I remembered??? Yes, oh yes, very very bad.
Where to start? The rooms are gloomy, the staff is indifferent. While the bed is comfortable, the bedding is too short to cover a 6'3" person from toes comfortably covered to the chin.
There is no air conditioning. They did supply a fan, but there is a curious problem with he Dorint - only one electrical outlet in the room is unswitched to the rest of the lights. So if you want to work on your computer and have the fan blowing, it's not possible without having some sort of electrical splitter. (Or you could keep the lights on and unplug one of the lights ...). Similarly, at night, unless you want to sleep with a light on, you need to unplug a few lights to have the fan operate on you all night (which was necessary).
The shower commits one of the ten deadly sins of travel - uneven water temperature due to other customer's usage in other rooms. The towels are the quality you would expect from a scuzzy "afternoon delight" hotel on the outskirts of Scranton, PA (yes, I have been there).
The internet is expensive and slow - further, it had some sort of firewall issue that caused me not to be able to connect with my VPN. Parking is expensive.
While the breakfast is good, it is very expensive. The Lunchtime buffet is extremely expensive and not terribly good. Of course, there are so many alternatives that one should only eat in the hotel if you're unable to get out (which I was awaiting a meeting).
On the good side, it is close to the water tower and many very good restaurants in Mannheim. However, if you really want to stay in this location, there are several very very good other hotels in the area.
And you get all of this for perhaps the most expensive price in Mannheim.
This review is the subjective opinion of a TripAdvisor member and not of TripAdvisor LLC