Best location, you can do everything walking from there. Oporto City Flats' office is right next to the building's front door which is amazing for check in/out and tips from the staff.
The appartment is very nice and comfortable. There's a balcony, which is a plus if you're a smoker. Everything was super clean. I'm happy I found an awesome adress to stay in Porto. I'll be back for sure :)