The flat is very central! Perfect!
For 6 people it is only to sleep (it's quite small though) but if you exploring Lisbon that's fine, though one of the rooms didn't have a window.....you have to walk though it to the next bedroom....depending who you are with that's not ideal (with kids it worked fine).
Unfortunately there is a building site next door at the moment which was loud in the morning....but there are lots of building sites in Lisbon at the moment.