The Fortaleza do Monte was not built by the colonial government. Construction began in 1617 under the Society of Jesus, the Jesuit order whose Portuguese missionaries had established a significant presence in Macau since the sixteenth century. The Jesuits wanted to protect their properties from pirates, and the hilltop location — directly east of what would become the Ruins of Saint Paul's — gave them commanding sightlines in every direction. The fort was completed in 1626. It did not remain Jesuit property for long: Francisco Mascarenhas, the first governor of Macau, recognized the fort's strategic value and took it over as his official residence. Governors would live within its walls until 1749.

The Dutch East India Company had long coveted Macau as a trading base, and in 1622 they sent a fleet to take it. The attack was serious — well-organized and well-armed. The Portuguese defenders were outnumbered and outgunned in many respects. What turned the battle was a shot from the Fortaleza do Monte's cannon. It struck a powder magazine on one of the Dutch vessels, triggering an explosion that broke the assault. The Dutch retreated. The fort had proved its worth in the only engagement it would ever fight. Thirty-two muzzle-loading cannon lined the fort's walls after that, and two watchtowers anchored the southeastern corners — a garrison posture maintained for the next three centuries, even as the actual threat steadily receded.

After the Dutch assault, the Fortaleza do Monte settled into the long administrative life of a colonial institution that outlasted its original purpose. Governors lived here until 1749. From 1810 to 1841, two companies of the Portuguese Prince Regent Battalion used it as a base to function as a police force. When that era ended, the fort sat as a restricted military area until 1965, when the barracks were converted into a weather observatory and the grounds were opened to the public for the first time. The Meteorological Department operated there for thirty years. In 1996 the observatory moved to Taipa; by 1998 the Museum of Macau had opened inside the old military buildings, giving the fort its current identity.

Today the Fortaleza do Monte is both a serious historical monument and a genuinely pleasant place to spend an afternoon. The tree-covered park at the summit offers panoramic views across the Macau Peninsula — the Grand Lisboa tower visible to the south, the dense urban grid of the older parishes spreading in every direction, and beyond them the Pearl River Delta and the hills of Guangdong. Replica cannon from 1860 line the walls, close enough in form to the originals to give a sense of how the fort once bristled with armament. The reflecting pool near the Museum of Macau lends the inner courtyard a surprising tranquility. The fort is part of the Historic Centre of Macau, inscribed as a UNESCO World Heritage Site, and surrounded by the ruins of Saint Paul's and the network of old lanes and churches that make up one of the most distinctive colonial streetscapes in Asia.