Campsites in this part of the Basque country are few and far between, so Zubizabala is a welcome find. It is about 40km south of Bilbao, and 20km or so north of Vitiora Gaseitz in the midst of quite striking hilly countryside.
Beware if approaching from Bilbao with a large caravan that the last six miles or so are quite steep with numerous hairpins, though the road is very well engineered. The road between Vitoria and the site is by contrast pretty level and easy.
The site has about 40 level pitches, all grass and all with electric hook-ups (unusually high amperage for Europe). The pitches are quite small, so cars are left in the parking area, and you may be in close proximity to your neighbours.
Toilet facilities are excellent, with separate male and female areas. The site opening season os quite short, mid June to mid September, and outside this time it may not be possible to contact for advance booking. The nightly charge for two adults, caravan and electricity was 30 Euros in 2012, so fairly expensive.
Julen, the owner, speaks very good English and will give you plenty of advice on the local area for walking, biking and sight-seeing.
We took his advice when we visited Bilbao and took the train from Lemoa - cheap and frequent, but Lemoa is about as ugly a town as you may wish not to find, and the rail trip is not picturesque! Nontheless, this is an easy way to get to visit the stunning Guggenheim museum. We were lucky to be there the time of the major David Hockney exhibition - magnificent.