This is a great apartment centrally located in the downtown historical center of Lisbon. Many major sites are within walking distance, and the water is just a few minutes away! This was a great place for 3 of us visiting Lisbon for a few days, and the apartment was very clean and spacious - perfect for a medium sized group (we all got our own room!). We arrived in town early on check-in day and had no problem storing our luggage securely with a hostel down the street.
Note that it is a 5th floor walk-up so expect to climb a lot of stairs. Also, before booking I would confirm with the host that there is no construction happening in the building during your stay. We were unaware that the floor below us was having construction (the host unfortunately did not communicate this to us, although he was very responsive otherwise), and so we were awakened at 8am every morning with the sound of hammers and saws below our rooms (not great if you like staying out late enjoying the night life of Lisbon!). I presume this is temporary, but it was really the only criticism I have of the listing and put a damper on our stay.