A sustainable energy visitor attraction, famous for allowing the public to take trips up its giant wind turbine, has suddenly closed.
The charity which runs the Green Britain Centre, near Swaffham, Norfolk, said the site was unprofitable.
It has welcomed hundreds of local school pupils every year to teach them about green energy sources.
The site has been handed to landlord Breckland Council, with the offer to help it find new owners or a new use.
The Green Britain Centre was run by The Green Britain Foundation led by Dale Vince – the founder of green power company Ecotricity.
The centre’s huge wind turbine was said to be the only one in the world you could walk up.
A spokesman for Ecotricity said the turbine, which provides power for 1,000 homes nearby, would still continue operating, as would some solar panels on the site.
After 10 years Mr Vince said the site was not breaking even and closing was the only option.
Mr Vince said: “We took responsibility for what was the EcoTech Centre about a decade ago – stepping in to save it from what would have been its third insolvency, because we thought it was a brilliant idea worthy of support.
“Despite our best efforts, we’ve been unable to bring the centre to something resembling a break-even position 10 years later.
“It’s with some regret that we believe we’ve reached the end of the road. It’s a particular shame for the many local schools that visit each year, but we just can’t make it work.”
A spokesman for Breckland Council said the authority was “surprised” by the closure.
“As the owner of the building and surrounding land, we expect to work closely with the current tenant through their notice period to ensure a smooth hand-over.
“We will also now consider opportunities for the best use of the site in the future.”