This could have been a five star review quite easily. The location of the apartment is fantastic — it's on a pedestrian mall downtown, within walking distance of anything you'd want to do in town. That part was great.
As for the negatives, the bathroom doesn't seem to be ventilated properly, so there was mildew growing on the grout in the shower. I would expect that to get scrubbed down regularly, but that was not the case here.
The worst part of our stay, though, was the lack of communication from our hosts. As it turns out, we were at the apartment at the onset of the coronavirus shutdown of Spain, and when it would have been very helpful to discuss the news with a native Spanish speaker, our host turned off his phone. Yes, completely off — I couldn't even leave a voicemail.
Had we stayed for the full duration of our reservation, we might have gotten stuck in Spain for some time. Fortunately, we got the information we needed from another source, checked out early, and managed to get to Barcelona for a rescheduled flight home before the Spanish government shut down everything — trains, hotels, you name it. The management of Marcial33 was absolutely no help with the situation. I expect better from a hospitality company.