Akademy/2013/Sightseeing
Bilbao has some very interesting museums, like the famous Guggenheim Museum or the Museo de Bellas Artes.
If you would rather hang out by the sea, there are a few beaches close by which can easily be reached by bus or the Metro.
Check out the website of the Bilbao tourist information which has all kinds of useful links.
You can also download an Android or iPhone app with tourism info about Basque country