Killian's place is highly recommended. It was in a great location and neighborhood, but also not loud from the street. As others have said the apartment building is above a school. But we were able to even nap in the afternoon during recess as the bedroom is a quiet space. GREAT rooftop terrace. Nicely stocked kitchen and nice bathroom. Also an easy 5 minute walk from the nearest metro station. If you need a nice cafe nearby - check out El Petit - one block down on Gran Via. We went twice (last two days) and I wish we had found it earlier in the trip! :)