Lisbon’s Tower of Belém has an exquisitely rich exterior with sculpted balconies and limestone ornaments. Its six-sided base has turrets at each corner, echoic of a Moorish style. Designed at the end of the fifteenth century to guard Lisbon harbor, the tower was commissioned by King D. João II, but construction didn’t begin until the reign of his successor, Manuel I, between 1514 and 1519. As the tower and its hull-shaped bastion were fully realized in cream-colored Lioz limestone, the fortress came to resemble a galleon petrified in stone. At the time, Belém was a vital launching point for Portuguese exploration abroad, as was reflected in the Manueline—or Portugal’s late Gothic—design. The naval-inspired exterior motifs to the vented casemate were designed to accommodate the new developments in sixteenth century artillery that helped to solidify Portugal's maritime empire. The tower's architecture represents an age in which Portugal was the first commercial and maritime empire in early modern Europe.
Conserving an icon for the Portuguese people
In 1994, we systematically identified and mapped deterioration and alterations found on each stone. Though the tower was stable, other problems had developed from air pollution and weathering caused by the harbor winds. The architectural sculptures at the base of the turrets were severely deteriorated from exposure, and although the tower’s outer stone surfaces were in a stable condition, they required cleaning to remove lichen and black crusts. The most crucial conservation issues concerned water ingress. The Lioz limestone, comprised of calcium carbonate, was vulnerable to erosion by acidic agents like acid rain, a process further affected the carved details decorating the tower, a problem successfully addressed.
The importance and conservation of the tower was summed up by Isabel Cruz de Almeida, Director of the Tower of Belém and Jerónimos Museum at the time, when she said, “It is now a cultural beacon, an icon reminding the Portuguese people and visitors from abroad of the country's rich and exciting heritage. What would the message be to the people of Portugal, if that icon were allowed to deteriorate?”