Expo.02 has attracted one million visitors in its first three weeks. One of the top attractions so far has been a unique creation resembling a cloud.
The distinctly atmospheric construction - created by New York architects Elizabeth Diller and Ricardo Scofidio - is wowing visitors to the national exhibition site at Yverdon-les-Bains.
The first of its kind, Diller and Scofidio's brainchild is a feat of design as well as engineering that has come at a price - SFr15 million to be exact.
Suspended over the lakeside at the end of a long, metal walkway, "the blur" is created by spraying water through more than 30,000 jets evenly spread over a 78-tonne structure.
Is it a cloud? Or is it a blur?
"It's an interruption in vision, a blur, a disturbance, an artificial weather system," architect Diller told swissinfo.
The public and organisers of Switzerland's national exhibition, though, have their own ideas about what the structure is. Dubbed "the cloud" because of the fog generated by the water jets, it has proven to be one of Expo's highlights.
"It's fantastic," enthused one young day tripper to Yverdon. "It's like being in the clouds!"
Disorientation by water
Visitors can choose to admire the blur from a distance or from within the installation itself - raincoats are provided!
"Sure there're places to buy raincoats so you don't want to get wet, but it's SFr2. If it was free, then I'd get one," said one young woman.
The New York duo hope visitors will lose their sense of perception and become disorientated when inside the giant structure.
"This piece is a-spatial, it's without depth, it's without mass, it's featureless, it's formless," said Diller. "Even though what you see is made out of steel and is very strong, it's actually extraordinarily lightweight. And once the fog goes on, it becomes hardly visible," she continued.
The cloud is more than a piece of art "that's flexing its muscles". According to its creators, it is an event: one that in the run-up to the opening of Expo has generated more headlines than atmosphere.
While the finished product is impressive, the blur has given its creators many problems.
First, they ran into trouble when micro-organisms from the lake clogged the blur's filters. Then the installation fell foul of local health authorities when regional government doctors ruled that bacteria in the lake could put the public at risk of contracting legionnaire's disease.
"We found ourselves discovering things that probably we should have discovered a year before," said Diller.
"For example, two and half years ago when the drawings went out to bid, there was a preliminary system design. They tested the waters and the plankton was one thousandth of the levels that are in the water now."
What the designers and engineers failed to consider was that at the time of Expo opening in mid May, the number of micro-organisms in the water would shoot up as a result of the first warm weather.
"But that kind of miscalculation was discovered way too late and so much of the system had to be rethought in terms of the filtration," continued Diller.
Fortunately, a solution was found so that the blur could be started up in time for Expo.02's grand opening on May 14. Tap water was used until May 29, when organisers were given the go-ahead to start up the filtration systems to clean the lake water.
"Me and the Universe"
The interaction of the "artificial weather system" with the 'real' weather offers an insight into Yverdon's theme of "Me and the Universe".
The exhibitions and architecture are all about how people interact with their environment, according Sergio Cavero, the site's artistic director.
"The architects tried to translate the theme into a sensitive landscape where the senses and sensuality become feelings. In Yverdon, their central preoccupation was to produce an experience - be it mental or physical," Cavero told swissinfo.
While the cloud is an example of this endeavour, Cavero said the Red Bar exhibition also illustrates the relationship between man and his surroundings.
"In the Red District, visitors can drink love potions in a bar that is completely decorated in red," explained Cavero. "As their perception adjusts, guests see only red."
When they leave the bar, everything appears green, "so we manipulate the perception and create a phenomenon".
The cloud with its 31,400 jets spraying water, is perhaps less subtle. Apart from getting soaked, the 25-metre-tall structure affords beautiful views of the Yverdon site and the lake.
Filtration problems aside, Diller and Scofidio's cloud has certainly added a silver lining to Expo.02.
by Samantha Tonkin