The Expo 2008 world fair on water and sustainable development has opened in the Spanish city of Zaragoza.
King Juan Carlos officially opened the exhibition on Friday. An estimated 6.5 million people are expected to visit the fair before it closes in mid-September.
Switzerland will have its turn to take centre stage when the fair celebrates Swiss day on June 27.
The Swiss pavilion includes presentations of national expertise on hydrology and pollution. A special display of water animals is aimed at attracting the attention of young visitors.
The government approved a budget of SFr3 million ($2.5 million) for Switzerland's participation.
The Expo features Europe's biggest fresh water aquarium, a 76-metre water tower and 140 pavilions themed around different climate zones and representing 105 countries.
Around 2,000 environmental experts will produce a "Zaragoza Charter" with recommendations for solving problems such as the lack of clean water and the danger of wars fought over water resources.
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