Thanks to Ana and Gloria. They give us all the information about the best way to arrive at the apartment and what to do and see in Lisbon (attractions, restaurants, quarters, etc.).
The apartment is at the last floor (3d) of a nice building, exactly behind Rossio square in a peacefull pedestrian square.....so no cars and traffic noises! The building is located at the end of a stairs but that's Lisbon! At less than 5 minutes you can reach underground or 28 line terminal so that's really good.
The apartment is really good and clean. Kitchen is well refurbished to prepare coffee, tea, or breakfast as you want. Supermarket is near, just 3-4 minutes walk. So you have all the necessary to spend a good stay. We think we'll use it again when we'll come back.
Thanks again!