Serafin's apartment was ideal for our short trip to Bilbao. The apartment is huge for 2 people and has everything you could need (and more) for a stay.
Serafin was a very welcoming host, who met us on arrival and gave us information on the town and the apartment. This information was very much appreciated as it gave us guidelines for where to visit/eat/drink for the duration of the stay.
The private parking so close to town (approx. 10 mins walk) made our trip very easy. There are plenty of facilities right across the road from the apartment (supermarket/cafe/restaurants) and is ideally located next to a metro stop if needed.
I would definitely recommend Serafin's apartment, not only due to it being a great place to stay but also due to the welcoming nature of Serafin himself.