The appartement is located in a very central part of Porto, only 5 minutes walking distance from Sao Bento and many bars right downstairs. Abel & Mariana's appartement is on the third floor, reachable by lift and is located in between two other appartements privately owned. The check-in is a little complicated the first time but assures a safe stay. Everything is very clean and wifi connection is stable allround. The addition of a dishwasher is also great.
I recommend going to Espaco77 for a cheap beer and heading over to Tito's II in Matosinhos for one of the best pieces of fish you'll ever have for an affordable price.