Construction has begun of the first large-scale hydro power scheme in Scotland for almost half a century.
An artist's impression of the Glendoe power station
Prime Minister Tony Blair ignited an explosive charge to begin the creation of an 8km tunnel in the hills high above Loch Ness.
The £140m Glendoe power scheme is the largest to be built since 1957.
The Scottish and Southern Energy project will mean the construction of a dam, a reservoir and turbines hidden in an underground power station.
Mr Blair, who was accompanied by First Minister Jack McConnell during a visit to the site, was later due to address the Scottish Labour Party conference.
Mr McConnell said the Scottish Executive was determined to put renewables at the heart of Scotland's energy future.
"Scotland has the wind, the waves and the tides to be among the world leaders in generating clean electricity," he said.
"Backing renewable energy is right for Scotland. It's right because we owe future generations of Scots facing the threat of global warming nothing less."
SSE said that while much of the project would be built in the hills overlooking Loch Ness and Fort Augustus, it would be virtually invisible when completed.
The scheme will involve the construction of a 1,000m dam at the head of Glen Tarff and the building of an underground power station inside Borlum Hill.
It will involve collecting water from a new reservoir, about 600m above Loch Ness.
The power station will produce about 180 million units of green electricity in a year of average rainfall.
Operating at maximum capacity, SSE said the scheme would be able to generate enough electricity to power 250,000 homes and should be fully operational by 2008.
It is hoped the construction phase could create 400 jobs.
Despite the national rush towards renewable energy, landscape and environmental concerns mean it is likely to be the last big hydro electric scheme north of the border.