Workmen mount scaffolding around the 17th century, 95ft-tall bronze canopy by Giovan Lorenzo Bernini surmounting the papal Altar of the Confession in St Peter's Basilica at the Vatican, Feb 21, 2024. (PHOTO / AP)

VATICAN CITY - The giant bronze-and-wood canopy in the middle of St Peter's Basilica is being gradually engulfed by scaffolding as Gian Lorenzo Bernini's masterpiece gets its first major restoration since the mid-1700s.

The almost 30-metre-high canopy covers the high altar of the basilica, and was built on the spot where St Peter, the first pope, is believed to have been buried after dying as a Christian martyr in the reign of Roman Emperor Nero (54-68 AD).

The holy year, also known as a Jubilee and held at least every 25 years, starts on Christmas Eve 2024 when the pope opens the Holy Door of the basilica

The altar, from which only the pope can celebrate Mass, is "the cornerstone of the entire architecture of the Basilica", Father Enzo Fortunato, head of communications for the church, said on Wednesday.

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The restoration project, costing some 700,000 euros ($756,000) provided by the Knights of Columbus Catholic Charity, was announced last month but actually started on Feb 14. It is set to be completed by late November, Vatican officials said.

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The structure needed special attention after "250 years of use and abuse", said Alberto Capitanucci, an engineer at the Fabbrica di San Pietro, the department in charge of the basilica.

He said clean up and repair works will pause during Easter week, to allow Pope Francis to lead celebrations for the most important festival in the Christian calendar, marking the death and resurrection of Jesus Christ.

A view of scaffolding around the 17th century, 95ft-tall bronze canopy by Giovan Lorenzo Bernini surmounting the papal Altar of the Confession in St Peter's Basilica at the Vatican, Feb 21, 2024. (PHOTO / AP)

The aim is to return Bernini's baldachin, as the canopy is known, to its splendor before the inauguration of the 2025 Holy Year.

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The holy year, also known as a Jubilee and held at least every 25 years, starts on Christmas Eve 2024 when the pope opens the Holy Door of the basilica. The event usually attracts millions of pilgrims seeking the remission of their sins.