This is a very well located, spacious studio-flat, smack in the historical centre (Ribeira), only 200 meters from the Douro river and in easy distance from Trindade and São Bento metro stations. The pictures are very accurate. Additionally, the wifi works like a charm and the kitchen is well equipped for casual cooking.
I was here on my own, but imho the flat easily fits 2 and even 4 people, if you don't mind using the couch.
Check-in and check-out went smoothly, and Paulo replied promptly to some practical inquiries.
Would definitely stay here again, next time I'm in Porto! (if it's your first time in Porto, make sure you bring your walking shoes though, streets are steep here! :) )