This place from Antonio & Luisa is really perfect, well situated near Trindade station, i.e. ideally situated in the center of the city. Connection to any place you'd want to go is fast and direct, the Douro river and Ponte Luís I bridge are within walking distance, with a Froiz supermarket nearby.
The apartment itself is very clean, good amenities and sufficient WiFi. Check-in and check-out were easily handled and straightforward.
I'd for sure return!