The apartment location is superb. It is right in the heart of Casco Viejo close to the hubub and excitement of Beautiful Bilbao and the wonderfully sociable Basque people. Miriam's and Elena's welcoming touches make all the difference. I immediately felt very welcome and at home. I stayed for a month, so this was important to me. They seem to have thought of everything.
I am a huge fan of Bilbao. Food, wine, culture, people, scenery. It has it all.
I would recommend the Attic and would definitely stay again.
My only word of caution is if you are very tall the sloping ceilings may be a challenge. I am 6' 2" and managed no problem. If you are much taller than this it may become a problem.
I liked the place so much it feels like a bit of a betrayal to write a negative comment, but it is relevant.
Overall 10/10. Superb.