Great place. Close to San Bernardo and Bilbao Metro Stations, in less than a 1.5km walk you get to Gran Via.
The apartment is small, perfect for 2 people, and have everything you need: well equiped kitchen (fridge, microwave, cooktop, pans, good cutlery, washing machine for clothing). The bathroom has a good shower, but no bathtub (for me, this is great!).
There is no lift in the building, but with only a few stairs you get to the place, so: no luggage carrying issues.
The only improvement point to notice is the mattress of the bed: a bit soft for me, what gave me some back pain after 5 days.
But all the staying was awesome. No check-in issues, the place is clean, I could cook some Spanish dishes and we could take a lot of nice tours by foot. I surely recommend.