A world-famous rock formation known as the "Azure Window" collapsed into the sea off the coast of Malta's island of Gozo Wednesday.

The arch, on which tourists were allowed to walk until recently, was one of the Mediterranean archipelago's most popular landmarks, according to BBC.com. At about 9:40 a.m. local time (3:40 a.m. EST) Wednesday morning, the sea claimed not only the arch – it brought down the entire formation.

"There was a big raging sea beneath the window," Gozo resident Roger Chessell told the Times of Malta. "Suddenly, the arch collapsed into the sea with a loud whoomph, throwing up a huge spray. By the time the spray had faded, the stack had gone too."

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In a series of tweets, Malta Prime Minister Joseph Muscat expressed sadness over the loss.

For years, geologists warned that the Azure Window was eroding rapidly, according to Reuters. Environment Minister Jose Herrera told reporters nothing could be done to prevent the collapse, but they were unaware the structure was in imminent danger.

According to a 2013 study, geologists concluded the Azure Window would eventually collapse, but it was expected to survive for several decades.

Many residents of the island went to the coast after news of the collapse spread and remained in disbelief after observing the scene, the Times of Malta also said.

"The Azure Window's demise should serve as an eye-opener to all concerned to look after and maintain and protect where possible, the touristic sites this little island has to offer," the Gozo Tourism Association said in a statement.

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