The town of Frutigen in the Bernese Oberland is currently a hive of activity preparing a fish farm for alpine caviar and a tropical greenhouse for exotic fruit.
Warm water from springs and the Lötschberg rail base tunnel is being used for the project.
Dmitri Pugovkin, who is a biologist from Siberia, catches an almost metre-long sturgeon in a net from the tank, grabs it forcefully but carefully and lays the wriggling fish on a board.
The researcher, who is working on the project for Bern University, uses ultrasonic equipment to determine the fish's sex.
"It is male and five years old," he says before sliding it back into the pool.
The water has a temperature of 20 degrees Celsius and flows directly from the Lötschberg base tunnel where it has collected over a 14-kilometre stretch until it comes out at the northern portal.
The temperature is ideal for the sturgeon, a fish species that is endangered because of the much sought after caviar.
"In Russian waters, the sturgeon lives at temperatures of two degrees in winter and up to 18 degrees in the short Siberian summer. In Frutigen, they have permanent Siberian summer conditions and thrive," says Samuel Moser, who is manager of the Tropic House (Tropenhaus as it is known in German) in the town.
When the sturgeon are killed, Swiss retailer Coop sells the fillets in its local stores. There are small quantities at present but the plan is for 20 tonnes to be produced annually.
The Tropenhaus is aiming to make big money with the caviar from the sturgeon females. It wants to produce two tonnes a year providing three-quarters of company revenues by the year 2017.
The fish installation, one of the few sturgeon farms in Europe, is the heart of the Tropenhaus. The sturgeon come from Hungary. The youngest is eight months old and the oldest is eight years and measures up to a size of one and a half metres.
The company behind the Tropenhaus aims eventually to produce its own breed of sturgeon.
"Protection against disease"
"That is the best form of protection against disease," Moser told swissinfo.
The warm water from the Lötschberg tunnel, he says, is not allowed to flow directly into the nearby Kander river.
"Particularly in winter, the 20 degrees Celsius water from the Lötschberg isn't really suited to the low levels of local waters. The biological rhythm of the endangered lake trout is disturbed."
The chairman of the Tropenhaus, Peter Hufschmied, launched the idea to use the warm mountain water to heat a greenhouse for exotic fruit and the fish farm in 2002, so that the water from the tunnel would not have to be cooled down, wasting energy.
Contrary to initial fears, local people welcomed the innovative project, with the idea also in mind that jobs would be created. Now, farmers in the region produce feed for the fish.
Construction of the site, costing SFr28 million ($26.4 million), started in May 2008 and is due for completion at the end of 2009. The Tropenhaus, only a few minutes away from Frutigen's railway station, is now taking shape.
Visitors can already have a glimpse of things to come inside a temporary greenhouse covered by plastic. Here they can see a dozen or more banana trees growing and a few coffee plants and papayas. It is foreseen that ten tonnes of exotic fruit will be grown here every year in an area of 2,000 square metres.
It is hard to imagine on this winter's day in the Bernese Oberland at 800 metres above sea level that tropical fruit will grow here.
However, Moser is optimistic. "We're not afraid of the competition. Unlike the usual tropical fruit that is available, we can allow it to ripen and serve or sell it in a matter of hours."
There will be a visitors' centre with a restaurant and an exhibition room next to the greenhouse, where the Bernese energy company, BKW, another main sponsor with Coop, wants to explain geothermal energy and other renewable energies to people.
Tropenhaus manager Moser says that other endangered species like the sturgeon will be exhibited in the hope that consumers will have a better idea of the fish when they go out shopping.
No Mystery Park
Moser is not worried that the Tropenhaus will suffer the same fate as Interlaken's Mystery Park - the brainchild of Swiss bestselling author Erich von Däniken, which closed two years ago in financial difficulty.
"We have a broad-based support; the Mystery Park was aimed solely at exhibitions. But we are involved in production and expect a substantial income from the fish."
Fish farming, caviar, research, renewable energies, sustainability and knowledge transfer, bananas and papayas... and all this in the Bernese Oberland.
Even though the intercity trains no longer stop at Frutigen as they speed through the Lötschberg, the tunnel provides the warm and clean water that will be used by the Tropenhaus.
swissinfo, based on an article in German by Gaby Ochsenbein
The project works closely with the Centre for Fish and Wildlife Health of Bern University for supervision of the fish stocks.
The sturgeon fish population is in danger worldwide and the species is under the supervision of Cites (Convention on International Trade in Endangered Species of Wild Fauna and Flora).
The production of caviar in fish farms reduces pressure on the wild species found in the Caspian Sea.
Peter Hufschmied launched the idea in 2002.
June 15, 2005: The people of Frutigen voted in favour of planning permission.
May 16, 2008: A ceremony was held laying the foundation.
The planned official opening is due to take place at the end of 2009.
The budget is SFr28 million.
About 50,000 visitors are expected every year.
Main sponsors: Coop and BKW Energy
A Tropenhaus already exists at Wolhusen in canton Lucerne.
Fish and fruit
The Tropenhaus in Frutigen says the fish farm is run according to the guidelines of organic aquaculture, respect for nature and animal welfare.
This means low density of fish stock, fish feed with minimal use of fish oil, and fishmeal and fishponds designed for the natural needs of the particular fish species.
It adds that the greenhouse production focuses on economically interesting fruit varieties such as banana, papaya, mango and guava.
Other species are used to optimise productivity and for demonstration purposes.