Begun during the reign of D. Sebastião (1557-1578), in 1570, under the supervision of João Gomes da Silva, diplomat and trusted man of the Court (designed by the master of fortifications Simão de Ruão, son of João de Ruão), it consisted of a simple bastioned structure, enclosing the hospice (monastery) and the Benedictine church of Santo Tirso (Old Church), old medieval structures. The bishop of Viseu, D. Miguel da Silva, built a church and an abbey palace on this site, for which he used the designs of the architect Francesco de Cremona recruited in Italy; Together with the São Miguel-o-Anjo Lighthouse (completed in 1527), which is only a few hundred metres away, they were the result of his patronage and constituted the first example of Renaissance architecture in the North of Portugal (the main chapel and nave of the church, with the inclusion of the bastioned structure and the dismantling of the roof, served as the parade ground of the fort).
With the Restoration War of independence, the remodelling of the fortification was required. Fearing a Spanish invasion along the northern border of the kingdom, King John IV (1640-56) in 1642 dispatched the new Chief Engineer of the Kingdom, the Frenchman Charles Lassart, to the city of Porto. He had the opportunity to see, in situ, the ineffectiveness of the seventeenth-century structure in the face of the offensive means of the eighteenth century, and he drew up a new project that expanded and reinforced it. The works were carried out by the Benedictine architect João Turriano.