I visited Guimarães from Porto. Just a day trip. It was one of the many UNESCO sites I would visit this road trip.
I loved the place! It was a Sunday and very quiet but made it easy for photography. Parking you can do best at the castle and from there walk to the palace of the dukes, then continue to Olive Square. Then circle back wandering the small streets with the medieval half wooden houses.
Highly recommended!! A photo gallery you can see on the link.