For me one of the best view for the city of Lisbon is this one: the view from the other side of the river, Almada, in Cristo Rei.
From this point of view you can see almost every part of the city, since Cascais until the city center and, if it’s a cloud free day, you can even see Sintra.
And for course you have this iconic view from the 25 de Abril Bridge that is well known for being always compared to the Golden Gate Bridge in San Francisco, USA.
For me this is also one of the best places to see the sunset once that you can see the river and the sun setting just above it, so beautiful and so worth it.
Here you can also enjoy a huge, and I mean really huge (20/30 km huge – depends on the weather), view over Lisbon and all the cities nearby which is as gorgeous as it sounds like!
You can go to the very top (110 meters) of Cristo Rei and enjoy this view. If you desire you can also see the Shrine that is visited every year by so many pilgrims.
Find more about the schedules and about the Shrine of Cristo Rei here.