Built in conjunction with the Jesuits from 1617 to 1626, this was the city’s principal military defence structure, and was crucial in successfully holding off the attempted Dutch invasion of Macao in 1622. The fortress was equipped with cannons, military barracks, wells and an arsenal that held sufficient ammunition and supplies to endure a siege lasting up to two years. In 1998 the Macao Museum was installed at the site, consisting of two underground levels and a third one above the fortress’ top platform following the location, volume and design of the old military barracks that existed at the site before the area was demilitarized in 1965. The designs of military structures in Macao inspired the southern Chinese authorities to start building fortresses of a similar kind to defend their extensive coastline.

Mount Fortress is built on top of Mount Hill, which rises 52 metres above sea level. The fortress covers an area of approximately 8,000 square metres, in the shape of a trapezoid. The four corners of the fortress protrude to form bulwarks. The northeastern, south-eastern and south-western 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. The parapets were crenulated for the installation of 32 cannons and the two corners of the southeast wall have watchtowers. The walls facing the Chinese Mainland do not have any battlements, indicating that the fortress was built only for defence against attacks from the sea.