Carlos's apartment was awesome, just like all the previous reviews have said. Everything you could want or need was available. The bed was very comfortable, the kitchen was large and well-equipped, and Carlos was a fabulous and helpful host. One of the best things he did was to leave a very detailed notebook explaining everything about the apartment, a list of nearby restaurants, and some suggestions for short day trips to the "hanging bridge" and Algorta. Both of these suggestions were spot-on.
While the apartment is quite close to the old town and the large Mercado de Ribera, it is up a big hill. But fortunately, there is a bus that goes up that hill and has a stop near the apartment. Be sure to get a Baixa card which allows for very cheap fares on buses and the Metro.
If we were to come back to Bilbao, we would love to stay in Carlos's apartment again. It's one of the best Airbnbs , out of many, that we have stayed in.