Located next to the sea, it is believed that the first fortification sited on the bar of the River Lima estuary dates from the reign of King Afonso III (13th century). However, the earliest certain date is the 15th century, when a fortress was built there that would have been completed in the following century, in the reign of King Manuel I. This is indicated by various Manueline architectural features, notably the 'Roqueta Tower' in the south-west bastion of the present fortress.
In the late 16th century, the fortress underwent a series of improvement works, having already been under Spanish domination in the reign of Philip II (Philip I of Portugal). And so the current fortress, with its polygonal floor plan, was built based on a design by Filippo de Terzi, the most famous architect of military buildings of that period.
References:The Church of St Donatus name refers to Donatus of Zadar, who began construction on this church in the 9th century and ended it on the northeastern part of the Roman forum. It is the largest Pre-Romanesque building in Croatia.
The beginning of the building of the church was placed to the second half of the 8th century, and it is supposed to have been completed in the 9th century. The Zadar bishop and diplomat Donat (8th and 9th centuries) is credited with the building of the church. He led the representations of the Dalmatian cities to Constantinople and Charles the Great, which is why this church bears slight resemblance to Charlemagne's court chapels, especially the one in Aachen, and also to the Basilica of San Vitale in Ravenna. It belongs to the Pre-Romanesque architectural period.
The circular church, formerly domed, is 27 m high and is characterised by simplicity and technical primitivism.