Lovely little city with enough to see and do to fill up 1-2 days. the city is flat and easy to walk around - there is a tram and metro network but we walked everywhere so cant comment on that.
Everything - really everything is shut on sundays so i would avoid being there on a sunday if you can plan it that way.
The city is great, I would always recommend taking the city tourist bus as it gives a good oversite to all there is to see in and around the city.
Nice transportation hub to Rioja wine region. You just needed 1 hour to travel to Haro or Logrono. The Guggenheim museum is very nice.
I hadn't expected Bilbao to be such a beautiful city. It was so easy to walk around, very pedestrian friendly.
There were wonderful squares, parks and fountains as well as other buildings of architectural interest, eg the Alhondiga centre. I also ate the best tapas of any city in Spain and can particularly recommend the cafe Iruna both for the surroundings and the food.
Bilbao is a vibrant city. Judging from the street scene, the happiness index of the city should be high.
It was a Sunday when we went to the city center. In the street, river bank and the park in the city center, young parents were seen out with their children having good time. Grand parents were around to join the family fun too. The city is clean and kept in good order. Love and happiness are in the air.