We had a Club Double with Terrace and the room size was good, with a nice large double bed, which was comfortable. The room we had is in an annex (no 537) which is connected via an inside passage. This does however not work for disabled persons, as it has several stairs in between.
The terrace is large, but seems not to be serviced as both table and stools were dirty.
The bathroom was a good size, but the curtains were half falling off.
Outside of the hotel there is no sign of Silken, so if you ask someone, do refer to Hotel Indautxu, otherwise no-one can help. In any case if you arrive by plane take a taxi, rather than the official airport-bus. It is much quicker, gets you directly to the hotel and costs no more than € 30.
We also did have drinks and a meal at the hotel which was both good and reasonable in price, considering it's a 4-star hotel.
There is however one thing that annoyed us. Contrary to other Silken Hotels we stayed at, they don't provide a WiFi code but ask you to register by name. This meant however that several times a day we had to login in again, for both our i-phones and i-pads which was really bad.
Location wise we struggled a bit with the hotel as the old town, Guggenheim Museum etc are all 15 minutes or more (walking) away. The taxis are however quite cheap (normally € 5) within town. For a next visit I would nevertheless consider a different location.