If you want to have a magnificent view of the whole city of Lisbon plus the 25th April bridge and the Cristo Rei all in one, just head to the Cais do Sodré ferry terminal and take the ferry to  Cacilhas.

For less than 2 euros you can go back and forth with stunning views.

Cacilhas terminal is an old place somehow ‎spoiled, but the walk west toward the bridge is really great (you can't get to the bridge by the sea, though).

At the eastern point, very close to the station, there's also a red lighthouse vith great views on the east part of the city.

 Do not miss it if you have 1 hour to spend.