Cristo Rei is a sanctuary that dates from 1959. It faces Lisbon and is around 110 meters high. From the top of the pedestal it is possible to see an amasing 360º view. In a clear day (and Lisbon has plenty of them) do consider to go there.
Costa da Caparica coastline is famed for its vast sandy beachs that span for more then 15 km. Many of them are loved by surfers It is very easy to access from Lisbon and is the prefered beach for people living in Lisbon, and certainly for those that live across the river.