Venice Builds Glass Barrier to Protect St. Mark’s Basilica from Flooding
By Esme Franks
St Mark’s Basilica in Venice is one of Italy’s most treasured cultural monuments. It is also highly significant in art historical terms; a considerable amount of Venetian history is represented in the story of its site, the phases of its construction and restoration, its architectural composition (a Greek-cross structure incorporating five domes, based on the sixth-century Church of the Holy Apostles, which once stood in Constantinople) and its opulent interior, covered with shimmering mosaics inspired by Byzantine iconography which present, through biblical scenes and cycles of the lives of the saints, the message of Christian salvation.
St. Mark’s Square Flooded in November 2019. Credit: Sky News
Underneath the celestial splendour of the high domes lies the basilica’s richly tessellated floor: 2099 square metres of marble and enamel in opus sectile and opus tessallatum, two ancient mosaic techniques. The former consists of different coloured marble fragments and the latter involves the shaping of small pieces with a chip hammer. Both methods are documented in Vitruvius, Varro, and Pliny, and demonstrate the wealth of the duchy; marble was precious, at once hard and colourful, and the operation required skilled craftsmen probably brought in from Constantinople or Byzantine Greece. The vast swathes of mosaic make up primarily symmetrical, geometric patterns which are interspersed with an iconographic program of figuration including birds and other animals.
Opus sectile: a floor mosaic representing an icosahedron attributed to Paolo Uccello, active at St. Mark’s between 1425 and 1433. Credit: https://www.the500hiddensecrets.com/italy/venice/culture/mosaics
These precious floors have been, however, under increasing threat from the city’s acqua alta (high water) which, until recently, had been regularly subjecting them to irreparable damage. In November 2019, for example, an especially disastrous flood caused the building, begun in 1063, to “age 20 years in a day”, according to Carlo Alberto Tesserin, overseer of the basilica’s historic preservation.
In an effort to defend St. Mark’s against further damage from the continuous flowing in and out of harmful salt water until the level of the pavement can be raised, the city of Venice has constructed a temporary glass barrier surrounding the entire building. It measures 1.3m high and was completed in November. It has stopped water from seeping into the building through its vulnerable outer marble walls, and spared it future catastrophe – for now.
The Procuratoria - the vestry-board (management committee) of St. Mark’s - decided as late as 2018 that the marbles and mosaics of the church could not go on unprotected, especially since the Venetian weather patterns have been growing more random and erratic throughout the last few decades. The project was designed by Mario Piana, the basilica’s architect, and Daniele Rinaldo, a highly respected local engineer. The urgency of the case is reflected in the barrier’s record construction time. The former director of the UNESCO world heritage site told The Art Newspaper that the solution is graceful and unobtrusive, incorporated seamlessly into the building and its surroundings.
The barrier works along with a complex system of valves and pumps that redirect the water back to the canals from the flooded drains. It is hoped that, in the future, the height of the Piazzetta’s waterside looking out toward San Giorgio will be increased significantly while the drains in St. Mark’s square will be modernised to cater for the predicted increase in flooding. The barrier has already cost the Venetian government €5.3 million.
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