“We went away for two days and what happens is that six years of sacrifice and work and love for what we’re doing was just washed away in a flood,” Valencia Colomo said, sloshing around her antiques art store in knee-high rubber boots and waders. “We’ve come back to nothing.”

Colombo’s store wares sit partly submerged in a few inches of remaining seawater, the force of which smashed apart furniture, carried away stock and somehow managed to move the location of the property’s stairs.

This New Orleans native and her husband, Giancarlo, are not alone in their dismay.

Venice declared a state of emergency Wednesday after floods, known locally as “Aqua Alta,” swept through the lagoon city, flooding its historic basilica, inundating squares and tearing through centuries-old buildings. The financial cost of the flooding is likely to run to hundreds of millions of euros, according to Venice Mayor Luigi Brugnaro.

A man wades in the flooded crypt of St Mark's Basilica on Wednesday. Manuel Silvestri / Reuters

The water level was two inches shy of matching the highest levels on record — the devastating 6 feet 4 inches surge of November 1966.

Floods like these pose an almost existential question to Venetians. How can they protect their city for generations to come?

It’s a question that plays upon the mind of Pierpaolo Campestrini, director of the Lagoon Research Consortium, which looks into problems facing the Venetian lagoon.

“We need a protection system for all of Venice,” Campestrini said as he showed NBC News where water poured into the crypt of the Basilica di San Marco, the most famous of Venice’s countless churches.

The salt water, he said, did immeasurable damage to the brickwork and accelerated its aging.

"In one single day, we lost 20 years," he said.