I only have one day in Porto, arriving around noon, and leave next day afternoon, so would really like to stay in the center (Riberia) if possible. I will have a rental car, and i don't want to take it to center after i read all the suggestion on this forum. How hard is to find an overnight parking space outside of old town? I read there are some garage near metro station, but seems they only provide max 12 hours parking, do they allow park overnight? how much normally would it cost? I am thinking to park at airport, but not sure if the travel time worth the hassle. Any suggestion is appreciated.