Up until about ten years ago, Bilbao was known as an ugly industrial city on a murky brown river. Then the Guggenheim came to town and the city has been systematically beautifying ever since. I found the areas around the river and the parks to be quite pleasant.
One more recent addition to Bilbao is this pedestrian bridge:
Frankly, walking on this bridge was scary, especially when it was raining. I'm not a phobic person; I'm okay with heights, etc. But walking on slick glass of a bridge with open sides was not my favorite activity. I never truly felt unsafe, but it gave me the willies.