Sergio's apartment is amazing. It is in a perfect location, close to everything, and in a very quite neighborhood.
It's in a walking distance of everything in the center of Lisbon, close to Castelo de Sao Jorge and to the metro and tram!
There are supermarkets near by, a lot of coffee shops and restaurants.
Sergio is very nice and helps you in anyway he cans.
100% recommend and I will stay there again if I came back to Lisbon. :)