The same way you shouldn't visit a volcano without either knowing about the geology of volcanoes or having someone to tell you about it, city tours give you more information to appreciate the city and should not be missed. Porto is a very walk-able city thanks to its small size, and the Wild Walkers have split the city into two tours, ensuring that you get more details in each tour. That you can pay as much as you can afford and think they deserve means the tour becomes accessible for a lot more people.
In particular Anna was a great guide, infusing her tour with energy and humour. She managed to engage the group while rattling off historical facts and curiosities, which is much better than what most history teachers can claim. She was very generous with recommendations for food, which makes it a pity that I can only eat so much in one day. Herding a group of adults across busy streets and narrow alleys is potentially more difficult than herding a group of kids, because we think we know better, but she did it well. I strongly recommend having her as your guide in you find yourself in a position to choose.More