Cleo’s place is in the heart of the city - 1 minute walk from La Rambla and in Gothic quarters. Also Port Vell and Barcenota beach are 5 and 15 minutes walk respectively, while the Plaça Reial (the well known central plaza surrounded by restaurants) is less than 1 minute away. Barcelona itself is a small city, so even Gaudi’s sites can be accessible by walk from the apartment if one is willing to walk for 20-30 minutes or more.
Also it may be helpful to not that all public transport and taxis are easily available at La Rambla.
The apartment is not very big - it is more like a continuous space where the bathroom is defined by a glass brick partition and the bedroom is separated from the rest of the space by a curtain. Thus privacy between the occupants may be limited. Also we were told that Barcelona city government no longer allows the entire apartments to be given to tourists for short stays, and thus you may only find part of the apartment for use to yourself - which was the case with this apartment - with one or more rooms locked away as private.
Cleo, the owner of the apartment, was very responsive and the communication with him was easy. Our wifi did not work the first day, and he was quick to correct it. Cleo also provided us helpful local tips and guided us when we wanted to book a taxi for the airport.