We spent a week at Sonia's apartment and enjoyed it a lot!
The location is perfect! I can't even describe how lucky I felt when every day after roaming the city i found myself close to home wherever we went. You can get everywhere you want to by feet. However if you prefer to use transportation subway is only 5 minutes away.
Inside Sonia provided us with everything needed: towels, microwave, a fan (thanks a lot!!), booklets describing the attractions of Barcelona, even some discounts. There was water, toasts and jam for us in the fridge as well as some tea and coffee,which was very thoughtful as we were very tired and quite hungry upon arrival.
We very greeted by a very nice girl and she showed us around. The place seems safe, the building gets locked as well as the apartment itself.
All in all we felt very welcome in the place we stayed. Hope that next time I am in Barcelona this apartment will be available.