Frederico's and Joana's flat is very conveniently located close to Baixa metro station and a 10 minute walk from Cais do Sobre train station. It is a lovely place in the middle of town from where you can get around really easily.
Frederico was very helpful in preparing for the trip and explaining on how to get to around. And his wife Joana who welcomed us to the flat also allowed to keep the luggage in a store room downstairs after check out that we did not have to carry it around until departure. Comes recommended.