We enjoyed our stay in Marios appartment very much.
It is located very central, perfect for a stroll through the city. Places further away were easyily accesable by bus.
The appartment was clean and spacious, the check in/out straight forward and flexible. At our arrival we recieved a map of the city center with tips for things to do, good bars, shopping and so on.
If we ever come back to Porto I would book it again.