Perched on a platform up in the air, two restorers are vacuuming the "sky". A quick wipe from a sponge follows and then a touch-up with a pencil. Little by little, the enormous clouds above The Hague are returning to their original colour.

Every two decades the Panorama Mesdag, the world's oldest panorama painting still on its original site, gets a facelift under the watchful eyes of visitors to the museum just outside the stately city centre.

Painted by the 19th-century Dutch master Hendrik Willem Mesdag from 1880 to 1881, the masterpiece gives visitors a 360-degree view of the beach at Scheveningen, a famous seaside suburb of The Hague, creating the illusion the viewer is standing right in the heart of the scene.

As in the late 1800s, sightseers today are still amazed by the three-dimensional quality of the cylindrical painting.

Visitors climb circling stairs to emerge in the centre of a purpose-built wooden rotunda, built on real sand that slopes down to the floor. Surrounded by the painting itself, the optical illusion is complete.

On the beach, flat-bottomed fishing boats are coming and going from the North Sea. Elsewhere on the sand, soldiers are riding their horses.

Look in yet another direction, and there's the fishing village of Scheveningen, with The Hague's tall church towers on the horizon -- as it was almost 140 years ago.

"We really believe we're at the beach in 1880," one Chinese visitor whispered. "It's very impressive."

- Phoenix rising -

But currently the restorers of the Mesdag are stealing the spotlight.

"Sometimes people even call out 'hello'," smiled Leonoor Speldekamp, as she gently wiped the dust from a church steeple gradually regaining its ochre colour.

"Some people visit the museum especially to come and look at how the work is being cleaned. When we're absent or on a lunch break, they're disappointed not to see us on the scaffolding," she said.

She also took part in the previous restoration mission 20 years ago. "There were holes in the canvas. It was badly damaged because a bird had destroyed a joint in the museum's roof, causing a leak," the restorer said.

That was the first time the painting got such a thorough cleaning. Before then it was "cleaned and restored occasionally," said Suzanne Veldink, a member of the Mesdag's management team.

Like a phoenix rising from the ashes every two decades, all of the Panorama Mesdag -- 14 metres (45 feet) high and 120 metres in circumference -- is being carefully cleaned, starting at the top where most of the dust gathers.

"There's no layer of varnish, which means the dirt, dust, soot and lots of things can penetrate the painting," Speldekamp said.

Time seems to stand still for the restorers as they remove dust with meticulous swipes and retouch colour with deft strokes.

- Major attraction -

The presence of the restorers, who blend into the painting's 19th-century landscape, is as unusual as it is inevitable.

"The Panorama Mesdag has remained a private museum and we cannot afford to shut down during the three months' restoration," said Veldink.

"For the public however there's real added value to the visit (at the moment). It happens only every 20 years, so it's very special to witness," she told AFP.

"We came on purpose to see the restoration of the canvas," said one art-loving visitor from Israel with her husband nodding in agreement who both declined to be named.

"It is impressive and very rare to see," she added.

One of the best-known painters of the time, Mesdag was assisted by friends in his greatest work. He also created and co-financed the museum, and even had the forethought to install rails on the ground to allow future restorers to move scaffolding around the painting.

It is now a major drawcard in The Hague, welcoming some 150,000 to 200,000 visitors per year.

Restoration work is expected to be completed by mid-September.

Source: AFP