Built between 1617 and 1626 by the Jesuits, the fortress one of the main defence structures of the city. It housed barracks, arsenal and storehouses to allow it to withstand a siege lasting two years. You can get good views of the central part of Macau Peninsula from here. The fortress can be accessed by escalator just east of St Paul's. The Macau Museum is located within the fortress (see "Museums" section below).

The Fortaleza do Monte (Portuguese for Mount Fortress, also Monte Forte; officially Fortaleza de Nossa Senhora do Monte de São Paulo, in English: Fortress of Our Lady of the Mount of St. Paul; Chinese: 大砲台; Cantonese Yale: daaih paau yìh) is a fort in Santo António in Macau. It is the historical military centre of Macau. The fort forms part of the "Historic Centre of Macau" and is a UNESCO World Heritage Site.

The fort was built between 1617 and 1626 on the 52-metre tall Mount Hill, located directly east of the Ruins of Saint Paul's. It was constructed to protect the properties of the Jesuits (mainly Portuguese Jesuits) in Macau, especially from pirates. Later, the fort was taken over by Francisco Mascarenhas, the first governor of Macau, as the governor's residence.

The fort occupies an area of roughly 8,000 square metres. Thirty-two muzzle-loading cannon were placed around the fort's walls, and the two corners of the southeastern fort wall have small watchtowers. The fort proved crucial in successfully holding off the attempted Dutch invasion of Macau in 1622.

The fort remained a restricted military area until 1965 when the barracks in the fort were converted into a weather observatory and the fort was opened to the public. The observatory ceased its function and was relocated to Taipa in 1996 before it was demolished to make way for the Museum of Macau, which was officially opened on 19 April 1998. The tree-covered park at the top of the fort has a panoramic view of the mainland area of Macau.