I just asked copilot (AI) and it came up with what looks like a good route:
Here’s a suggested itinerary for your holiday in Northern Spain by train, starting in Barcelona and ending in Bilbao, with your first stop in Madrid. Since you have a 6-day Interrail train ticket, we’ll make sure to use those travel days wisely.
Day 1: August 14 - Barcelona
- Arrival in Barcelona: Spend the day exploring this vibrant city. Visit La Sagrada Familia, Park Güell, and stroll down La Rambla.
- Overnight in Barcelona.
Day 2: August 15 - Barcelona to Madrid
- Train to Madrid: Use your first travel day to take a high-speed train from Barcelona to Madrid (approx. 2.5-3 hours).
- Explore Madrid: Visit the Royal Palace, Prado Museum, and Retiro Park.
- Overnight in Madrid.
Day 3: August 16 - Madrid
- Full day in Madrid: Continue exploring the city’s attractions, such as Plaza Mayor and Gran Vía.
- Overnight in Madrid.
Day 4: August 17 - Madrid to León
- Train to León: Use your second travel day to travel from Madrid to León (approx. 2-3 hours).
- Explore León: Visit the León Cathedral and the Basilica of San Isidoro.
- Overnight in León.
Day 5: August 18 - León to Oviedo
- Train to Oviedo: Use your third travel day to travel from León to Oviedo (approx. 1.5-2 hours).
- Explore Oviedo: Visit the Oviedo Cathedral and the Archaeological Museum of Asturias.
- Overnight in Oviedo.
Day 6: August 19 - Oviedo to Santander
- Train to Santander: Use your fourth travel day to travel from Oviedo to Santander (approx. 2-3 hours).
- Explore Santander: Visit the Magdalena Peninsula and the Santander Cathedral.
- Overnight in Santander.
Day 7: August 20 - Santander to San Sebastián
- Train to San Sebastián: Use your fifth travel day to travel from Santander to San Sebastián (approx. 3-4 hours).
- Explore San Sebastián: Enjoy the beautiful beaches, such as La Concha, and try some pintxos in the Old Town.
- Overnight in San Sebastián.
Day 8: August 21 - San Sebastián
- Full day in San Sebastián: Continue exploring the city and its surroundings.
- Overnight in San Sebastián.
Day 9: August 22 - San Sebastián to Bilbao
- Train to Bilbao: Use your sixth and final travel day to travel from San Sebastián to Bilbao (approx. 1-2 hours).
- Explore Bilbao: Visit the Guggenheim Museum and the Casco Viejo (Old Town).
- Overnight in Bilbao.
Day 10-12: August 23-25 - Bilbao
- Explore Bilbao: Spend the remaining days exploring Bilbao and its surroundings. You can take day trips to nearby places like Getxo or the Basque Coast.
- Departure from Bilbao on August 25.
This itinerary allows you to make the most of your 6-day Interrail train ticket while exploring some of the most beautiful and culturally rich cities in Northern Spain. Enjoy your trip! 

Is there anything specific you’d like to know more about or any adjustments you’d like to make to this plan?
It’s a way off your route, but I loved Seville, and of course Granada for the Alhambra. BTW, Barcelona to Madrid is not long at all - only 2.5-3 hours.
Sitges near Barcelona is a well-known gay-friendly resort, and hosts a massive Pride, if that’s your thing. I’ve never been though. There are some good LGBT and LGBT-friendly bars in the Eixemple neighbourhood of Barcelona, and Spain itself is pretty gay-friendly as far as I know.
Both Bilbao and San Sebastián-Donosti are great cities. There’s narrow-gauge railway that links the two (not included in the pass, but not expensive).
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Bear in mind most trains in Spain will require seat reservations. That makes a pass not as useful in Spain as it is in other countries. Details of reservation costs and how to make them on the Seat61 website.
https://www.seat61.com/interrail-and-eurail-reservations.htm#Spain
You’ll also need to leave a little time at stations to pass through security. It’s nothing like airport-style, but many long distance / high speed trains have luggage x-ray before boarding.
I don’t know if you have a first or second class pass - if first class, it’s well worth paying the extra for an inclusive meal on the AVEs.
Hi @ralderton ,
Thanks for the great reply. I have been to Barcelona and Sitges a few times as well as malaga & torramolinos. I will probably explore more of southen Spain another time, but this time i want to explore the north a bit.
I know i had to get reservations, but the link you shared has helped me understand how this works, and that it is not as simple as i was hoping. Thanks for the advice about the security… i had no idea.
I am going second class, so no inclusive meal option for me..
Thanks again :-)
Once you're in Spain, the reservations get easier: if you can't do it online, you can always do it at a station. (Barcelona Sants is often very busy, try another station if you're near one)
@ralderton ooh thank you