If you want to see a beach in an urban landscape, you have to go to Spindle beach (just take IC8 towards Castelo Branco and follow the signs to Castanheira de Pera).
There is nothing to equal it!
imagine a beach with palm trees, sun hats from palm branches, lounge chairs and even “real” waves produced regularly by powerful machinery. Great for the whole family, especially if you have kids. Children under 6 years old are admitted free.
Of course there’s also a fine bar and restaurant where you can have lunch there if you decide to spend here the day.