We have a free section in the motorhome park. It's worth mentioning separately since many people look specifically for free services. It's easy to miss because it's located next to the paid section.
There is a large parking area by the peaceful Douro river where we stayed for 3 nights. Two of them were very quiet, but on the third night, there was a long dog concert that went on late. It's unfortunate that some campers don't know how to control their dogs. There are toilets available 50 meters away, open during the day by the Douro river, as well as a facility to drain grey and blackwater and access to water.
Nice and well-located camper van area for visiting the city. There was a morning rehearsal of a band nearby, which was enjoyable and probably a rare occurrence as it only happened once during our two-night stay. The only downside is a lack of shade. Additionally, a great nearby activity is taking a boat to Pinhao and returning by train from the conveniently located train station.