I have used Airb&b many times and staying at Marta and Cesc was the best experience! Their apt is beautiful, clean and in a convenient location. A few minute walk from Sagrada Familia and metro. There are lots of restaurants, pharmacy and convenience stores around. We always felt safe in the neighborhood.
From booking, to checking in and out, everything ran smoothly with great communication. After booking, I received emails from them with lots of information about the apt and Barcelona which was really helpful. We got to Barcelona early in the morning where Marta greeted us at the front door. Marta was so sweet to explain things to us and answered all of our questions. They were always available via WhatsApp during our stay. We texted them to ask questions and for restaurants recommendations. They always replied right away. The only thing to be aware is there is no elevator and need to walk up 3 flights of stairs. Bringing suitcases up and down was a challenge.