The fort was built between 1617 and 1626 on the 52 metre-tall Mount Hill,located directly east of the Ruins of St. Paul's.It was constructed to protect the properties of the Jesuits in Macau,primarily from pirates.Later it was seized by the governor for the defense of Macau.
It occupies an area of roughly 8,000 square metres, in the shape of a trapezoid with an average side length of around 100m.The northeast, southwest and southeast walls are built on 3.7-metre-wide granite bases. The walls, 9 metres high narrowing upwards to 2.7 metres wide at the top, are made of solid rammed earth, further strengthened by a thick stucco of ground oyster shells. 32 cannons were placed around the fort and the two corners of the southeast wall have watchtowers.They were crucial in successfully holding off the attempted Dutch invasion of Macau in 1622.The walls facing the Chinese mainland are primarily built of granite and do not consist of any battlements, indicating that the fortress was built only for defence against attack from the sea.
The fort was a restricted military area until 1965 when the barracks in the fort were rebuilt into a weather observatory,and was opened to the public.The observatory ceased its function and was relocated to Taipa in 1996,then it was demolished to make way for the the Museum of Macau,which was officially opened on April 19th 1998. The tree-covered park at the top of the fort has a panoramic view of the mainland area of Macau.
Apart from being a fortress,it has served various functions: