Santo amaro docks is a really good choice for the city traveller, who wants just to relax and have a drink during his/her day. Personally I enjoyed the view of the bridge (ponte 25 de abril) and of the Tagus river while drinking a nice cold beer. It is a nice stop if you are going towards Belem or returning from there (a nice 20-25min riverside walk to the Discoveries Monument). You can easily reach the docks by train (Alcantara station), train or bus. I did not manage to visit santo amaro at night, but it seems as a good place for dinner, as the options are plenty.