Visit the castle above town
The castle gives a useful introduction to Castro Marim's frontier position. Its hilltop setting offers views across the surrounding landscape, while the archaeological displays add context to what you see from the walls. Allow enough time to look at both the site and its setting rather than making this only a photograph stop.
The climb is part of the visit. Choose a time when walking uphill suits the group, and avoid arriving with an itinerary so tight that anyone feels hurried over uneven ground. If you want a gentler day, make the castle the principal outing and leave another heritage stop for a future visit.
Follow the town's defensive story
The municipality identifies the Revelim de Santo António, castle and Fort of São Sebastião among the main heritage points. They help explain a town whose importance was linked to the border and its approaches. Choose a route through the centre that connects a few places you want to understand.
Do not treat every interior as an essential part of the circuit. The outside spaces and views can be worthwhile in their own right, with a guided visit useful if history is a particular interest. The municipal heritage programme uses advance arrangements for group visits, so plan a guided outing separately from a casual walk.
Discover the salt landscape
Salt pans and marshland form a different attraction from the fortifications. An organised interpretation of traditional salt production can help you understand the working landscape as well as its birds. Ask what the visit includes: a walk, an explanation of the process or a particular activity will shape the time needed.
For an independent nature outing, use the designated routes rather than following any track visible between the pans. The reserve contains sensitive areas and working land. Bring binoculars if you have them and be content to watch from a distance; a closer photograph is not a reason to leave the route.
Add the coast deliberately
The wider municipality includes the beaches around Altura, Verde Lago, Praia Verde and Cabeço. These are coastal outings from Castro Marim town, not features of the hilltop centre. Choose one access point and allow time for the road journey, parking and the walk over the dunes.
A heritage morning and a beach afternoon can work well when the journey between them is settled. If you would rather spend most days on the sand, a coastal base may suit you better, with Castro Marim as a visit. Making that choice early keeps the holiday aligned with what everyone wants.