We really loved our stay in Marcia's apartment. It is equipped with everything you might need, the check in/out was really comfortable and the communication with Marcia was great as well.
The apartment is located in the heart of Porto. When you step out the door there are plenty of cafes and restaurants, little shops,... Also the train station is nearby and you can reach the river by foot in 10 minutes. We really enjoyed our stay and I can definetly recommend the apartment.