King D. João IV ordered the ravelin to be built on the Rocha do Zambujal Hill to the east of the town, with a connection to the castle and fortress. This small fortification stands over the Guadiana and was built for the purpose of keeping watch over the estuary of the great southern river. 

Did you know? In 2009, the military structure of the ravelin was rehabilitated and a support structure for tourism in the municipality was created: the Centro de Interpretação do Território (Regional Interpretation Centre). The centre serves as a starting point for cultural itineraries and boasts a natural and virtual viewpoint that gives you a 360º view of the entire municipality. 

The St. Anthony Ravelin is a smaller fortificatiom but strategically vital, erected by Joao IV. in the hill of Rocha do Zambujal connecting to both the ancient Castle and the Fort of St. Sebastião. Given its location it served the purpose of controlling the course of the Guadiana. Inside it was built the Chapel of St. António, a baroque building of architectural quality, with chancel square bounded by strong pillars-corners.

This historic complex was sent build in Castro Marim at the beginning of the Restoration War (1640-1668), it was in the last decade target of one of the most sublime project of rehabilitation of the historical and cultural heritage, called Rehabilitation of St. Anthony Revelim Hill.

According to words of the architect Jose Alegria, author of the intervention project, this is a "structuring work in terms of location with a privileged connection to the Sapal Nature Reserve of Castro Marim / VRSA and terminating a strong Mediterranean architecture symbology" .

Completed in 2008, the reclassification allowed the rehabilitation of the military structure of the Ravelin, benefiting the entire surrounding area with paving, installation of equipment for information and visitor rest, but also rehabilitate the chapel and the mill. They were also built support structures for cultural activities, supported by a cafeteria and toilets, and finally proceed to landscape improvement of the whole hill of Ravelin.

The complex consists of:

. Regional Interpretive Center
The Territory Interpretation Centre is a reception space visitors and simultaneously starting point for itineraries and visits to the territory of the municipality of Castro Marim and Lower Guadiana.

. Windmill
Windmill operating in accordance with the original technique.

. Biological Garden
The St. Anthony Ravelin also has an educational garden to offer visitors a knowledge of traditional gardens.

. Andalusian garden
The leisure area includes a large green area with trees and shrubs, which highlights the Andalusian garden with an area of ​​4000 m2, a pleasant and healthy space for the enjoyment of visitors.

. Amphitheater free air
Another important element of this place is the outdoor amphitheater with a capacity of 500 seats in which you can enjoy good cultural shows.

. St. António Chapel
 The Chapel of St. António, a baroque building of architectural quality, with chancel square bounded by strong pillars-corners, was also submitted to the architectural complex of the rehabilitation process of Santo António Ravelin.

. Cafeteria