The stay at Robertos place was very nice. He offered me a super flexible check in and check out time, so I could do more things as initially expected.
The appartement itself was small but had everything I needed. One room with the bed, a kitchen and one bathroom... all for private use. A tram station is quite close to the building and the San Mames Metro station is also not far away.
I can recommend Roberto and his wife as host.