Most tourists spend a day at Bilbao. If you have only a day, make sure it is not a Monday because the must see Guggenheim Museum is closed on Mondays.
How many nights in Bilbao?
One day is adequate for you to get quick view of Bilbao highlights. If you arrive the previous evening that is even better so you can go out to eat in the Old Town or in Garcia Rivera. During the full day you can split between the Guggenheim and the Historic City centre
You should devote the first day for Guggenheim and the Historic City center. On the second day, you should visit beaches outside Bilbao and maybe do the Punta Galea cliff walk. In the evening you should see the Bizkaia bridge and return to Casco Viejo for dinner. It is not that Bilbao has a very sedate nightlife.
Three days is the perfect amount of time to see much of Bilbao. You can take in the unique art and architecture, eat plenty of pintxos and learn what it really means to be Basque. On the third day, you should go on an excursion.
Useful tips - Bilbao visit
For your ideal Bilbao trip of 1 or 2 days, here are some suggestions.
Budget to spend 150 euros a day as a couple. Accommodation 60 – 80 euros, food and drink 50 – 70 euros, Guggenheim entrance 20 euros for two including audio guide. Bilbao is not very expensive.
Start with Guggenheim: The main attraction of Bilbao is better seen as soon as possible on your trip. Many visitors just want to admire the building, which is a real work of art. You do not need to book tickets in advance.
Transport is easy in Bilbao. The city has an efficient metro and tram system. And once you are in the old city and Guggenheim areas, everything is a walk anyway. The Bizkaia card is not worth buying. The main city is connected by the tram (Euskotren Tranbia) and tickets are a flat 1.5 euros.
With more than a day, keep aside time for a visit to Vizcaya bridge. This is a unique structure, not seen in other cities. With a morning, you can also consider combining the bridge visit with the Punta Galea Cliff walk.
Accommodation is not a problem in Bilbao; you can stay anywhere that suits your budget. The city is safe and convenient to get around.
Main Bilbao attractions
In one day in Bilbao you should visit the Guggenheim Museum in the first half and then spend the second half in the Old City historic Centre.
In the new city Ensanche de Bilbao
Visit the Guggenheim Museum, travel on Norman Foster's Bilbao Metro, and walk through Philippe Starck's Alhóndiga a renovated wine cellar now a culture and leisure centre, if you like the concept of old buildings being reborn. If you like more museums, go to the Museum of Fine Arts.
In the old city Casco Viejo
Cross over the Nervion river and walk around Casco Viejo for the atmosphere, and see the Arriaga Theater opera house built in a neo baroque style. I don’t think you will have time to watch a performance so see it from the outside.
Away from the main Bilbao city
Go to the viewpoint of Artxanda for restaurants with views, use the funicular railway from downtown Bilbao to get there. See the Bridge of Bizkaia, a UNESCO listed industrial revolution icon, in Portugalete, north of Bilbao. You can also take a boat trip on the Bilbao estuary.
Getting around Bilbao:
The whole Bilbao center (old and new) is pedestrian access only, including The Guggenheim Museum, the Casco Viejo, the Museum of Fine Arts, and the shopping area. And you can take the efficient metro that runs throughout the city.
There are also guided tours of the city. All this can be seen in public transport and on foot. There is a tour bus that runs through the city with explanations in English, but it is not needed.
Attached is a link that I find very interesting to visit Bilbao, in 1, 2 or 3 days.
Never more than 2 days in Bilbao!
Bilbao is worth only 1 day of a 4 days Basque Region visit. Make sure you have 2 days for San Sebastian and 1 day for a Rioja itinerary.
Visitors to Basque ask if they should spend more time in Bilbao or San Sebastian. Even on a longer trip it is not worth spending more than 2 days in Bilbao.