You must ideally spend a week in Basque country but even 4 days is a good enough time to see the region.
IDEAL (1 week) : San Sebastian 2 days, La Rioja 2 days, Bilbao 1 day, French Basque 1 day, flexible 1 day. Here is a practical itinerary.
TYPICAL (4 days) : San Sebastian 2 days, La Rioja 1.5 days, Bilbao 0.5 days.
SHORT (2 days) : ONLY San Sebastian and around.
Spend 4 full days to get the best of the Basque region.
With 4 days you can also hop across to see the French Basque country.
Less than 2 days
It is not worth going all the way to the Basque region for 2 days. With only 2 days you will need to choose between La Rioja - Haro, Laguardia, Marques de Riscal (or) Bilbao and around (or) San Sebastian and around
Three full days
With 3 days in Basque region you can spend one day each in Bilbao and San Sebastian, and you can spend a day in the La Rioja wine region. But it will be rushed and you will not be able to properly appreciate the Basque countryside or see the French Basque country. With proper planning, you can get a basic flavor of Basque country in three days. But be prepared to put in long days.
A 4 day trip is ideal for the Basque country. Spend 2 days (a day each) in Bilbao and San Sebastian. It may be a little rushed depending on how much you want to see in Bilbao, but it is practical.
Spend 1 day in La Rioja - you can visit Haro, Marques de Riscal and Laguardia all in one day. I suggest start with Haro and end with dinner along the Laguardia city walls. Spend 1 day in French Basque country - St. Jean de Luz, Biarritz, and if you have time drive through Bayonne on your way back. With an early start this can be done, it is a unique experience to be in Basque country on both sides of the Spain-France border.
If you actually have 5 days to spare, spend another half day in Bilbao city and the other half around the cliffs of northern Bilbao - Getxo, Punta Galea, Sopelana - there is a cliff walk which is breathtaking.
More than Five days
With more than 5 days, you can explore the lesser known parts of the Basque region, the cider houses in the countryside and maybe even drive to Pamplona.
Where to go in basque country
(Must Go) San Sebastian : Even if you are not into glamour and style, you must go to San Sebastian. Besides being a stylish city, highlights of San Sebastian are its beaches, the surrounding Basque countryside, pintxos (basque tapas) bars, and Michelin restaurants.
(Next priority) Rioja : The wines here are world famous but go to the Rioja region for the architecture of the wineries and the luxury hotels attached to them, especially the Marques de Riscal in Elciego. You must definitely go to the walled, hill town Laguardia. Spend a night there
(Last) Bilbao : Bilbao is a one attraction town. Go only ion you have a day to spare. Without the Guggenheim Museum not many would come here. You will realistically only spend half a day at the Guggenheim. If you have another half day, there is good food and nightlife in the old quarter Casco Viejo.
My advice is to skip Bilbao
Instead, go to French Basque Country and spend a day in Biarritz for surfing and glamour, and Saint Jean de Luz for food and architecture.
At a minimum, you must spend 5 days in Basque country. In fact, the region offers so much that many visitors even spend 10 days.
If you are staying in Basque country for less than 10 nights, limit your itinerary to the most important parts of the region :
- San Sebastian
- Rioja wine region
If you travel in the week of 6-14 July, include Pamplona in your itinerary to watch the famous running of the bulls.
Note: Stay in 2 places at most. Otherwise, you will end up spending your time packing and unpacking.
My pick is to first base yourself in San Sebastian. Hire a car and do day trips to explore the Basque country and make sure to visit towns on both sides of the border with France.
At San Sebastian, reserve your nights to shop and explore the foodie scene in the old town. Be sure to go on a pintxos crawl . If you are into beaches then San Sebastian has excellent beaches too. My favorite beach in all of Spain is La Concha beach.
Consider staying overnight at the quaint town of Laguardia, to explore the wine region of La Rioja. To visit the wine region, hire a private guide and work with them to craft your itinerary.
Finally, it is always best to exit Basque Country from Bilbao. By ALSA bus, Madrid Barajas airport is only four hours away.