A 1.2-metre-high glass barrier has been suggested as a way to protect the 11th-century monument and its priceless mosaics from the acqua alta, or high tide, which regularly inundates the lagoon city.

The announcement comes after basilica’s revered marble and gold-leaf mosaics were swamped with sewage and the crypt left under a metre of corrosive salt water during record flooding last year, which peaked at 1.87 metres on November 12.Officials have warned that the basilica may not be able to withstand a repeat of the damage caused during the flooding.
The plan for the barrier, which would be built around the front of the basilica, has preliminary approval from city officials. The proposal now needs approval from the city’s heritage authority and its public works committee before it can go ahead.The glass barrier “would replace the iron railings that already exist to keep visitors away from the external walls,” Pierpaolo Campostrini, also a Procurator of the Basilica, told Italian daily La Repubblica.
St Mark’s Square is the lowest-lying part of Venice, and the most vulnerable to high tides. It starts to flood when the acqua alta reaches 85 centimetres and is completely underwater at 100 centimetres. However, the narthex of the basilica sits at an even lower point, and begins to flood at just 66 centimetres.