Old pictures of the Azure Window in Dwejra portray a sturdy structure which could easily stand for a thousand more years.

But the famous natural arch, which collapsed into the blue waters beneath last Wednesday, had been decaying at a fast pace, its shape altered drastically over the past three decades.

The ‘window’ developed through sea and rain erosion of a cliff face over a period of about 500 years. Considered one of Malta’s main tourist landmarks and most ecologically important areas, it was included in a Special Area of Conservation and, in 1998 was included on Malta’s tentative list of UNESCO World Heritage Sites.

The most noticeable changes in the shape of the arch took place on the upper slab. Sizeable pieces of it fell into the sea in the 80s, 90s and noughties, with the result that the arch was significantly widened.

(Top, and above - the Azure Window in the 19th century)

In April 2012 a large slab of rock on the outer edge of the cavity collapsed, further increasing the size of the window. Another rock fall occurred in March 2013.

Some of the smaller incidents were captured on camera, including a piece that came tumbling down as a cliff diver jumped over the edge of the arch last year.

In a 2013 report geologist Peter Gatt had found that much of the horizontal part of the arch, around 90% in fact, had collapsed during the past 30 years. He had also warned that parts of the sides of the arch are also fractured and prone to collapse, even if these do not affect the stability of the Azure Window.

Dr Gatt had warned that large chunks of the pillar were also prone to collapse into the sea and warned about the presence of fresh cracks on the south side, which he said needed to be monitored. He had recommended monthly readings of several cracks and the possible use of small bolt rocks.

Back then it was believed that the Azure Window would survive, at least for a couple of decades.

But unknown to everyone was the fact that the pillar, seemingly the sturdiest part of the arch, had eroded greatly underneath the sea. The strong waves that lashed at Gozo over the first part of last week proved to be too much and the entire structure came crashing down.

The Azure Window, used countless times as a backdrop for film productions, is no more. Nothing remains of the structure above sea level.

The government has now announced that it will issue an international call for expressions for ideas, and has mooted the idea of raising pieces of the window and putting them on display, an interpretation centre or even a digital augmented 3d structure.

Photo taken in August 2016 by Joe Demanuele

Just sea - a photo taken by Matt Hush on the day the Dwejra Window collapsed.