Huge parts of central Venice were engulfed last week by disastrous floods, with water suddenly rising over 180cm above mean water level. Climate change has been blamed for the unprecedented flooding, which is the worst to have struck the city in 53 years.

Venice is on its knees… the art, the basilica, the shops and the homes, a disaster,” lamented Luca Zaia, governor of the Veneto region, before the second acqua alta hit on Friday.

At one of the most iconic buildings in Venice, St Mark’s Basilica, the crypt became half filled with water and the antechamber flooded to a depth of 70cm. The cathedral is the best-known example of Italo-Byzantine architecture, filled to the brim with dazzling gold mosaics, marble floors, and valuable Old Master paintings. This is only the second time in a century that the 1,000-year-old structure has flooded.

We are essentially unable to protect ourselves,” said the engineer Pierpaolo Campostrini, one of the basilica’s procurators.

Venetian mayor Luigi Brugnaro said St Mark’s had undergone “grave damage,” although he offered no specific details. The 12th-century marble floor has perhaps sustained the worst long-term damage from the salty waters of the Adriatic Sea.

Unlike plumbing and electrics that can be repaired easily, submerged bricks and marble across Venice will gradually erode if not treated immediately. “When salt permeates the materials of these buildings, it crystallizes, and ascends vertically once the weather gets drier,” described Kobi Karp, principal at Kobi Karp Architecture & Interior Design.

Alongside local businesses, homes, and schools, the storm also directly impacted other Venetian heritage sites. Many museums and galleries were forced to shut as 80% of the city lay under water.

The Museo Archeologico Nazionale di Venezia remained open for as long as possible, having tweeted: “High tide? No problem if you are triton or a nereid! For the record: we are open, and we are waiting for your visit despite the awful weather.” But the catastrophic high tides eventually forced the museum to close.

According to a spokesperson for the 58th Venice Biennale, “due to the exceptional bad weather and extreme tidal conditions,” the art exhibition also temporarily closed during the floods.

Top attractions including the Accademia, the Ducal Palace and Correr Museum, announced that no works of art had been damaged following the floods, although several electrical fires were triggered at the International Gallery of Modern Art Ca’ Pesaro.

Specialists estimate that the city has borne at least €1 billion in damage (£857 million) after the first wave of floods, but this amount is likely to climb once an official survey has been conducted. The sheer number of cultural treasures at risk, in Venice and beyond, will only continue to rise as the consequences of climate change become increasingly evident.