Marta and Alberto's apartment is a great location for exploring the lovely district of Principe Real. I've been to Lisbon a number of times and this is definitely one of the nicer places to stay. The apartment is perfectly scaled for a single traveller, such as myself or a couple, and there are numerous amenities and a beautiful park close to the apartment location. As with all places in inner Lisbon, just be prepared for a bit of hill climbing - but that is the charm of the city. Definitely recommend!