Belém Tower

In the late 15th century John II laid out a defence for the mouth of the Tagus resting on the fortresses of Cascais and of São Sebastião at Caparica, which did not close the river. The chronicler Garcia de Resende, whose Crónica de D. João II appeared in 1545, wrote that the king judged Lisbon's defences inadequate and ordered a strong fort where the Belém tower now stands; John II died before anything was built.

Manuel I revisited the proposal twenty years later and ordered a fortification on the northern bank at Belém; in 1513 Lourenço Fernandes wrote to friends of the king's intention to build a tower near Restelo Velho. The design went to the military architect Francisco de Arruda, named Master of the works of the Belém stronghold. Work began in the mid-1510s — 1514 by Portuguese accounts — on a basalt outcrop off the shore, using stone also being cut for the Monastery of Santa Maria de Belém; in 1516 deliveries began of 763 blocks and 504 stones from the treasurer, Diogo Rodrigues. A 1,000-ton man-of-war, the Grande Nau, guarded the estuary until the fort was ready. Completion is given as 1519 in some accounts and 1520 in others. Gaspar de Paiva, at first stationed there temporarily, became the first Captain-General on 15 September 1521, and the fortress was named the Castle of St Vincent after Lisbon's patron saint. It was the first Portuguese fortification with a two-level gun emplacement.

Guides have claimed the tower stood in mid-river and was left near the shore when the 1755 earthquake redirected the Tagus. The Ministry of Culture and the Institute of Architectural Heritage record instead that it was built on a small island opposite Restelo, and that development extended the shoreline southwards until the tower was absorbed into the riverbank.

In 1571 Francisco de Holanda advised the crown to improve the capital's coastal defences, suggesting that the Belém tower "should be strengthened, repaired and completed…that it has cost so much without being completed". In 1580, after a few hours of battle, the garrison surrendered to Spanish forces under the Duke of Alba. After that defeat the tower's magazines gave way to cells, and its dungeons served as a prison until 1830, holding political prisoners under Philip II of Spain and later under João IV — among them Sebastião de Matos de Noronha, Archbishop of Braga, imprisoned for siding with Spain against João IV. In 1589 Philip I of Portugal had the engineer João Vicenzio Casale design a fort to replace the "useless castle of São Vicente"; it was never built.

A plaque dated 1655 in the cloister recorded the tower's work as a customs and navigation control point, vessels paying a tax as they entered the harbour. Under Miguel I (1828–1834) the dungeons held his liberal opponents, while another level served as a custom house until the duty on foreign ships was abolished in 1833.

French detachments were quartered in the tower from 1808 to 1814 during the Peninsular War; after they withdrew, Lord Beresford advised strengthening the batteries flanking its bastion. Under Maria II, Almeida Garrett protested at the building's decay and, with the Duke of Terceira's backing, the military engineer António de Azevedo e Cunha renovated it in 1845–46, demolishing the Philippine barracks raised over the bastion in the late 16th century and adding revivalist work such as the armoured merlons and the niche with the Virgin and Child. A beacon was installed on the south-east terrace in 1865–67 and a telegraph service started.

The tower was classified a National Monument by decree of 10 January 1907. It passed to the Ministry of Finance in 1940, which carried out small conservation works; the military quarters on the battlements were removed and the inner cloister built. In 1983 it hosted the 17th European Exhibition on Art, Science and Culture and, in the same year, was classified by UNESCO as a World Heritage Site together with the Jerónimos Monastery.

In the 1990s the property passed to the Instituto Português do Património Arquitectónico, which ran a full restoration from February 1997 to January 1998, reinforcing the tower and bastion, propping the south balcony with steel rods and resin and treating the statues of Saint Vincent of Saragossa and the Archangel Michael; the work took a Europa Nostra award in 1999. In 2022 the tower recorded 377,780 admissions. Its place on the register of the Seven Wonders of Portugal dates from 7 July 2007.