Everything other reviewers have said is true.
1. Sofia is a great host, will greet you in person and be in contact throughout your stay if you need any recommendations or help.
2. The flat itself was better than I thought, with a beautiful dining room and decorated throughout with nice art and little surprise messages throughout the rooms.
3. Location is perfect if you like a bit more quiet relaxing stay in Belem (otherwise you should stay in Lisbon for the hustle and bustle and energy)
4. Location is a few mins walk from the main Belem train station (with frequent, short ride in to Lisbon center)
5. Location is also a 10min walk away to the waterfront and the Padrão dos Descobrimentos monument and the tower of belem. 10mins walk to the famous Pastéis de Belém for the pastel de nata.
Great stay and you don't really need to think twice for booking.