I experienced many different guesthouse and I can say this one is one of the best I've been too.
I mean the location is just perfect, the apartment is very charming and the terrace is "increíble".
Beds are confortable, rooms are not too crowded.
Karla is a very nice and open minded person.
Definitely the guesthouse you must go to.
Volveré por mi próxima estancia en Barcelona.