Opera magazine
2026-01-09
The restoration of the mosaics on the vault of the Florence Baptistery
An impressive and innovative restoration project to bring new life to 10 million mosaic tiles
Now underway for three years, the major conservation site dedicated to the restoration of the magnificent 13th-century polychrome mosaics with gold backgrounds covering the dome of the Baptistery of San Giovanni in Florence is today fully operational. The intervention, planned over a total duration of six years, represents the first comprehensive restoration of the mosaic vault in more than a century, following the last major campaign carried out between 1898 and 1907.
The more than 1,000 square metres of mosaics—composed of approximately 10 million polychrome tesserae, ranging in size from 5 to 20 millimetres per side—are currently undergoing a complex conservation process aimed at recovering the structural stability of the surfaces, improving the adhesion of the mosaics to the vault, halting ongoing deterioration, and restoring the full brilliance of the gold background and the vivid colours of the glass tesserae.
For the first time in recent history, the public has been able—and continues to be able—to observe the mosaics of the dome at close range. Executed on preparatory drawings attributed to artists such as Cimabue and Coppo di Marcovaldo, the mosaics are dominated by the monumental scene of the Last Judgment and unfold, across four narrative registers, the Stories of Genesis, Joseph, Christ, and Saint John the Baptist. This extraordinary and unrepeatable experience is made possible exclusively during the years of restoration, through a programme of special visits launched in 2023 and still ongoing.
The construction site and the conservation intervention are commissioned and funded by the Opera di Santa Maria del Fiore, in agreement with the Archdiocese of Florence, under the high supervision of the Superintendency of Archaeology, Fine Arts and Landscape for the Metropolitan City of Florence and the provinces of Prato and Pistoia. The construction site was designed by the Opera di Santa Maria del Fiore and realised in collaboration with Tecno System Appalti and Layher S.p.A., while the conservation work has been entrusted to the Centro di Conservazione Archeologica, which counts among its most renowned restorations the celebrated mosaics of the Monastery of Saint Catherine on Mount Sinai. Since 2014, the Opera has already carried out restoration campaigns on the exterior of the monument and on the interior mosaic decorations, investing a total of €4.6 million; a comparable amount has been allocated to the restoration of the dome mosaics, bringing the overall investment to €10 million.
In order to restore the mosaic vault of the Florentine Baptistery, it was necessary to design and construct a technologically innovative scaffolding system capable of providing access to the entire surface of the dome—over 1,000 square metres—while minimising visual and structural impact at ground level. This solution allows visitors to continue admiring the walls and the scarsella, richly decorated with marble and mosaics, whose restoration was completed in 2022. The mushroom-shaped scaffold rises to a height of 31.5 metres, with a diameter of 25.5 metres and a walkable surface of 618 square metres at the upper level, while occupying only 63 square metres on the ground. Constructed with 8,150 elements, the structure employs state-of-the-art aluminium beams (Layher Flex) which pass through the square openings overlooking the attic level of the Baptistery, ensuring an even distribution of loads on the monument’s supporting structure.
The restoration of the mosaic dome—unexamined and unstudied at close range for more than a century—builds upon the experience gained during the previous restoration of the Baptistery’s interior walls and on the documentation of earlier interventions, particularly the campaign carried out by the Opificio delle Pietre Dure between 1898 and 1907. Investigations conducted over the past three years have confirmed a complex conservation scenario: approximately 344 square metres of ancient mosaic set on original mortar, partly affected by detachment; 567 square metres of mosaics removed and re-set on cement mortar during the late-19th-century restoration; and 128 square metres of reconstructed surfaces, following 19th-century losses, first treated as decorated plaster (1820–1823) and later remade in mosaic during the most recent restoration.
Diagnostic campaigns, initiated during the early phases of the project and still ongoing, have made it possible to assess the condition of the tesserae, the composition of the materials, and their overall state of conservation. The data collected—graphic, photographic, and scientific—allow the conservation team to define ever more precisely the most appropriate methodologies for each specific issue, identifying compatible materials and innovative technical solutions for the continuation of the restoration work.
Dominated by the monumental figure of Christ the Judge, the mosaics of the Baptistery dome were a powerful source of inspiration for Dante’s depiction of Hell in the Divine Comedy. According to the inscription in the scarsella, work began around 1225, likely with the involvement of mosaicists from outside Florence and furnaces already active elsewhere. Over the course of the century, however, Florentine artists achieved full technical and artistic autonomy, and by the end of the 13th century the dome was entirely clad in its dazzling mosaic decoration. Several generations of artists succeeded one another on the scaffolding, creating an extraordinary anthology of medieval pictorial and mosaic art, which also includes the vault of the scarsella, executed while work on the dome was still in progress. Once this colossal enterprise was completed, the mosaic decoration was extended to the wall surfaces as well, although these had not originally been envisaged in the initial design.
The Scope of the Restoration
This marks the first major restoration of the dome mosaics in over a century, following the last intervention between 1898 and 1907. The project covers over 1,000 square meters of mosaic surface, composed of an estimated 10 million polychrome tesserae (ranging from 5 to 20 mm per side). The primary goals are:
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Structural Stability: Securing the mosaics and ensuring their adhesion to the vault.
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Degradation Control: Halting ongoing deterioration processes.
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Aesthetic Recovery: Cleaning and revealing the original splendor of the gold background and the vivid colors of the glass tesserae.
Innovative Scaffolding: A Technological Marvel
Restoring the Baptistery's vault presented unique challenges. A technologically advanced scaffolding system was designed and built to provide access to the entire mosaic surface while minimizing visual impact at ground level.
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Design: A mushroom-shaped structure rising 31.5 meters.
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Working Area: Provides a vast upper platform of 618 square meters.
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Ground Footprint: Occupies only 63 square meters on the Baptistery floor, leaving the lower areas largely unobstructed.
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Technology: Utilizes cutting-edge aluminum beams (Layher Flex) distributed through existing openings, ensuring load is spread evenly across the monument's structure.
Historical Significance and Artistic Heritage
The Baptistery dome mosaics, dominated by the imposing figure of Christ the Judge, famously inspired Dante Alighieri's depiction of the Inferno in the Divine Comedy. Work likely began around 1225, initially involving artisans from Venice, but Florentine artists soon mastered the craft. Created over several generations, these mosaics feature preparatory designs by masters such as Cimabue and Coppo di Marcovaldo. The narrative unfolds across registers depicting scenes from the Last Judgement, Genesis, the stories of Joseph, Jesus Christ, and John the Baptist.
Key Facts & Figures:
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Restoration Duration: 6 years (2023 - 2028)
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Mosaic Area: Over 1,100 sq meters
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Tesserae Count: Approx. 10 million
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Scaffolding Height: 31.5 meters
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Ground Footprint: 63 sq meters
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Total Baptistery Investment (since 2014): Approx. €10 million.
The restoration of the Florence Baptistery's dome mosaics is a monumental effort to preserve an invaluable piece of world cultural heritage for future generations. While the temporary suspension of ground-level viewing is necessary, this project ensures the long-term survival and appreciation of one of Florence's most breathtaking artistic treasures.
