We had a really comfortable stay during a mad conference rush in Lisbon. The appartment is on a quiet street which is a privilege in Lisbon, since noise insulation in buildings isn’t great. You can reach Barrio Alto super easily with the delightful tram in the corner while you grab a snack at the tram station.
The appartment is a climb - so bad knees watch out. But then watch. Out for a lot of Lisbon :)