You just don't go to quaint Porto and its environs to dig up a large shopping center and,…read morefurthermore, even patronize it. However, my hat is off to ArrabidaShopping.
I found it because it sits within walking distance from the Mercure Porto Gaia Hotel, where I have stayed, along with other hotels, on a promontory above the Rio Douro where the ring road crosses it on a beautiful arched bridge called Ponte da Arrabida. Also, if you use transit to the hotel(s), you may be getting off your bus (the 902 or 903 from the Casa da Musica Metro, which is a quick ride) at or near ArrabidaShopping.
ArrabidaShopping sort of follows the American model. It has 3 levels, connected by stairs and escalators, inside an atrium setting. There is every kind of shop you might need. There are cinemas. There is a food court at the north end on Level 3. And guess what? If you go through that food court, you might have a tough time deciding where to eat because the choices are many and the food is good. Also, the roof is raised at the food court, and there are clerestories and such which make this upper level feel very airy and a nice place to take your time eating your meal.
You will be surrounded by locals. That much I promise. Also, European centers differ from American and Canadian centers in one major regard - they don't have 3 or 4 different department store anchors. Oftentimes, they are anchored by a super-duper supermarket ... in this case the Continente ipermercado, or hyper-market.
If you need to go to a shopping center in the Porto area, I would choose this center over El Corte Ingles on Avenida da Republica or Maia Forum, which is further out toward the airport. Not only that, if you take a walk outside, you can savor the beautiful setting and promontory which ArrabidaShopping occupies.