We booked this hotel through booking.com and we paid around 80 euro/night, then our expectations for the week in Barca were not as high. When we reached the hotel was a good surprise: we had a double room with additional bed for my son and the room was very spacious and clean, as well the bathroom. We visited, even if not tried, the top roof swimming pool; terrace view is amazing. We have not tried breakfast, since expensive, but we've been suggested by hotel staff to go to the bakery/pastry close to the metro station, fantastic breakfast, I extend to everyone this suggestion.

Me and the Mrs stayed here for a long weekend and can't say a bad word against it. The room and hotel itself were spotlessly clean and very nice place to be. The staff were very friendly and helpful, the spa was lovely, the views were great and it was reasonably priced. Also the Metro station is a 2 minute walk or you can just jump on a tram litterally outside the front doors!

I stayed in Barcelona for business at the end of October 2012 and was pleasantly surprised by the excellent efficiency and unassumed luxury of Hotel Diagonal Zero. Experienced friendly staff on all their rotations and the lobby bar is worthwhile for a good cocktail. Breakfast is standard and the choices are numerous and cater for most. The outstanding feature I would say is the wonderful spa in the basement of the hotel, prices are good and facilities excellent. Rooms are spacious and modern. Wi-fi free in the hotel - my room had a bad signal but I always carry a small Wi-fi router that I connected to the fixed ADSL line in my room which solved my internet connection. The hotel is 3 minutes walking from the nearest underground station and from there you can get to virtually anywhere. Will recommend !

This hotel seems to be more orientated for business trips, if you are looking for a hotel to enjoy with your family, then this hotel is not the best option.
It has good sides like the Mall nearby with lots of restaurants and coffee shops, also the tram was right in front of the hotel and just after a few minutes walk we were at the beach.
I was just a bit disappointed with the outdoor pool, it may be ok at the summer time but not so practical if the weather is cold or raining.