My worst experience of all with AirBnB! (in years of regular travels). So bad that I had to leave the flat after one night (despite I had two more ones booked, and I lost all the money).
Long story short, there is not a single positive note about this aparment: tiny, claustrophobic (sealings 2 meters high, literally not enough space to confortably undress), dirty (used napkins and years-old dust under the "bed"), run down (the bed is not even a real bed, but it rests on pallets; the walls are dirty and everything is ruined by the house cat that scretched all the surfaces with its nails). Fianllu, it is located in a dangerous and very noisy area (there are groups of drunk people shouting and peeing if front of the window mosy of the night on a Wednesday).
Moreover, at our arrival the cat of the house found a way to our room, jumped on the bed and on the pillows and hid under the bed, where it was very difficult (and disgusting due to the dirt) to take it out.
Final anecdote: in our trip from the airport, the taxi driver told us proudly that finally the center of Lisbon has been renovated and there is no more danger to go out at night anywhere. Yet, when we arrived in front of this flat he started swetting and immediately recommended us to go inside and never cross the alley in front of the flat if we didn't want to be robbed.
By the way, I have been in other 3 rooms/flats in Alfama (same district) all of which offered a wonderful experience in the same price level.
In summary: don't go there, there is not a single good feature, all you can find is for the bad.