If you are staying for a week in Lisbon, you should have time to visit Setúbal, a smaller city, 1 hour away by train (~10€ for a one way ticket). I wanted to get out of the city and take in some nature and beaches, even though I was there in winter. I have spent 3 nights in a wonderful hotel: Alcaçaria do Bairro very close to the city center. Here is what I did during these 2 days:
Birdwatching in the Sado Estuary
Setúbal is rather close to the Sado Estuary Natural Reserve (Reserva Natural do Estuário do Sado).
The Tourist Information : Casa do Turismo Setúbal (where there is a giant cat on the roof), gave me the name of a small business offering boat tours on the Sado Estuary: Passeios MiraSado. You can just give them a call and Carlos Miguel (he speaks very good English) will let you know of the time of the tour if there’s one. I went in winter, a really good time for birdwatching, but a really bad time for public transportation apparently. I took a Lyft (similar to Uber) to get to the Mourisca Water Mill : Moinho de Maré da Mourisca, the departure place. Once there, you get into a small boat with other people and you go around the estuary with very knowledgeable comments and see an amazing variety of birds, including flamingos !
Praia de Albarquel
If you need some beach time, it is doable, even better in winter, Albarquel beach is very pretty and quiet, and you can access it easily from the city !
You will go through Albarquel Urban Park on the way, which I’ll detail below.
Parque Urbano de Albarquel
This park is really fantastic, it has an amazing variety of plants and trees, huge eucalyptus (they were flowering when I was there) and some cats wandering around. I stopped there to enjoy the quiet and it was perfect!
If you have more time and a car, do not hesitate to check out the Arrábida Natural Park which seems to have stunning landscapes of beaches and cliffs !