Spain’s Basque Country

Without a car, I think Bilbao is the best option for a base, because it will have the best transportation connections. Anywhere else you stay will be less convenient for the day trips you want to take. Bilbao will also give you the most options of lodging types to fit your budget.

You can fly direct from Porto to Bilbao, and use this very walkable city as your base for the first three or four days. We do not have national parks in the Basque Country (although around 70% of its surface is covered by forests), but natural parks and protected areas of special environmental interest, like Reserves of the Biosphere.

If you stay in Bilbao, hiking from this city is very easy and you can be hiking in a very short time, no car needed (Pagasarri and Ganekogorta mountains are a very popular hike). I would also recommend the area around Durango or Elorrio (easy public transport there), mainly the Urkiola Natural Park, plenty of hikes there. Or the area around Urdaibai Reserve of the Biosphere, a beautiful area with also bird watching, or hikes from hermitage to hermitage with fantastic views.

If you stay around Donostia/San Sebastian, the flysch at the Geopark in Zumaia is a beautiful hike. The portion of the Northern St James Camino from D/SS to Pasai Donibane is a very popular hike too. But plenty inland too, my favorite one is the one starting at amazing Arantzazu Monastery to the impressive mountains of Aitzgorri Natural Park.

In Rioja Alavesa, the Basque part of the wine region of Rioja D.O.Ca, you also have wonderful hikes, like the Water Path of the Inglares River or the monastery of Toloño.

But, again, there are hundreds of hikes in the Basque Country, so a Google search will surely be of more help.

If you have 2 weeks, it is easy to go between Bilbao and San Sebastian/Hondarribia with
public transportation. Maybe a few days in each. I think you can get to French Basque towns
with public xport as well, but it may take a little more doing.