We spent a great Christmas time with my family!
Location was perfect, in the city center, very close to Barro Alto and Alfama. The city center is very touristic, but the steet of the apartment is very quiet (not noisy at all during the night). Flat was very clean and big enough for 14-15 people. We initially planned to stay at 17 (it would have been possible), but finally my uncle & aunt decided to stay at the hotel to have more space.
Communication with Joao was very easy! I definitely recommend this place to big groups!