If you are staying in Lisbon with a large group, stay here.
The apartment is well located no more than 20 mins outside of the old town.
Taxi's/Ubers are inexpensive if you want to make your way into the centre of town or to the airport.
The apartment itself is large and modern. It was spotlessly clean when we arrived and our host had arranged for a neighbour to meet us and show us around which was very helpful.
There are 3 ensuite bedrooms and a 4th bedroom adjoining the master (bear this in mind when booking.) The master is incredibly nice whilst the other rooms are somewhat basic in comparison so be prepared to toss a coin/argue.
There is a fully kitted out kitchen for when you want to make a meal and the apartment is around the corner from a small independent supermarket that has everything.
Down the hill you reach the waterfront (5 mins run/20 mins walk) and the can sightsee within Belem lots of beautiful monuments.