This place is pretty perfect. From the windows you see the castle and if you look right from the balcony, there is Tagus river at the end of the street. We spent two jet-lagged days here and we able to see most sites and eat good food. Taxis are easy to get to get to Belem. There are plenty of restaurants and coffee shops right outside the door. The parallel street is also a walking street and restaurants are somewhat cheaper.
The apartment itself is as pictured. It’s not big, but has everything you need for a short stay. The beds are firm. Stairs walking up to 4th floor are not bad if you are in decent shape, even our kids (5 and 8) did not complain.