I found it really intriguing that Porto reminded me of Lisbon so much, since they're not at all the same. Despite some locations having the exact same name, the other obvious similarity I found was the fact that these are both riverside cities.
We went from São Bento's station and walked around all day, visiting the Palácio de Cristal (where a bookfair was taking place) and enjoying the wonderful view we could get of the city. Then we descended to the Ribeira before going back again.