Moinho de Maré da Mourisca sits out in the Sado Estuary reserve, where Setúbal's city edge gives way to mudflats, reeds, salt pans, and big skies. The old tide mill has been restored as a small interpretive stop, and it works best as part of a slow morning with binoculars rather than a quick monument tick.
Go for the setting as much as the building. Boardwalks and paths around the mill put you close to herons, flamingos in season, and the quiet geometry of the estuary; it is also a good counterpoint to the beaches and cliffs of Arrábida. You will need transport or a bike to make it comfortable, but the reward is a side of Setúbal that still feels practical and salt-stained.