I stayed in Casa Formosa for more than a month. I had a wonderful time; Joao and Sara were extremely friendly and helpful. They know the city very well and can give you advice if you are looking for something to eat or something to see. I also liked the carefully selected vintage furniture in the rooms. The location of the apartment is great; it is at the center of the city with all the major sights and several subway stations in walking distance. Shops are also close by and there is one of the famous markets in the city at the corner. I believe this place with these hosts is the perfect accommodation in Porto. Highly recommended!