We stayed at Diana Hotel as a couple, first reserving 4 nights and then canceling the stay after one night.
The hotel is located in the best location possible, close to all the attractions we were planning to visit on our trip to Schwarzwald. Unfortunately, when we arrived we found out a few things about the hotel:
• It was very old, and the furniture and utilities showed.
• The small balcony was for some reason shared with the rest of the floor, so that other guests could easily peep into our room through the window (whose curtains cannot really be closed shut).
• A wasp somehow managed to enter the room, while it was closed. As we preferred not to get stung on our trip, we asked the staff for help. The employee simply killed the insect and wished us a good night, while leaving us with the body laying on the floor.
• The bathroom wasn't very clean, and we were surprised to see a shower curtain in a hotel's bathroom.
So for summary, it wasn't for us. But some might find this hotel great for their trip, though I still think that objectively the price of 100€ per night is too high.