I got an other apartment which was a lot larger and fancier than the studio, as far as I can see from the pictures. The place was nice with typical Portuguese decorations and a chimney. It was close walking distance to Rossio and the city center. However getting there with a luggage was a bit difficult due to the typical streets of Lisbon and because it is located a bit uphill.
As I learned later Airbnb’s do a lot of harm to the residents of Lisbon because flats and houses are being bought off by big companies / hotel chains and prices for living have risen 3 times in the past 2 years. So many residents can not afford to live in the city anymore. I think that Antonio’s apartments / studios might also be used only for Airbnb purposes and therefor booking it might be contributing to this problem. I’m not sure though. Next time I book an Airbnb I will definitely check that beforehand.