In short: We highly recommend this apartment and it's host. Perfect for young travelers, specifically couples or singles who want to be close to the action but come back to a quiet, small, cozy apartment on a private hidden street.
In more detail:
Catarina's place is charming, quite compact but very nicely put together and organized. The Apartment itself is in a semi private ally that is accessed through a door in the street so it really gives a great feeling of quiet and privacy, with some local families and a few other airbnb apartments in the alley. We really loved that part of it.
The apartment itself is very small but has all the basic amenities. They really managed to cleverly squeeze in everything in such a small space: 2 TV's, washing machine, kitchen with an oven, air-conditioning and more...
It was a bit too small for our family (couple + 5 year old) but for 1 person or a couple it would be perfect and really great value!
Catarina as a host was really great. She is extremely responsive and sincerely cares about her guests' satisfaction. We mentioned to her that there were a few basic cooking utensils that we would have preferred to have because we like to cook "at home" while on vacation. A few hours later there was a bag outside our door with everything we mentioned! Wow! :)
The area is also great. Lots of restaurants and parks, all within walking distance. This neighborhood is sitting on a few hills so you often have to climb very steep uphill streets to get somewhere but many parts of Lisbon are like this. It's part of the charm of the city, but maybe good to know if some of the guests are older or disabled.