Porto is a great city and Mario and Ana`s apartment are literally across the street from Sao Bento central tain station. Everything you need to visit is walkable from there, and the apartment is very cosy and clean.
Mario met with myself and my girlfriend at the airport and provided us the keys along with tips regarding places to visit, restaurants and activities.
Would highly recommend this apartment, and I would definitely contact Mario and Ana again if I`m back in Porto. Great experience overall!