Four mini-climates and more than 10,000 plant species will flourish in what it is claimed will be the world's biggest botanical gardens at Bodelva, near St Austell.
The grant was announced in Cornwall by one of the millennium commissioners, the astronomer Heather Cooper, who described the Eden project as "absolutely mind-boggling".
"I am absolutely amazed at the scale of it and I think it is marvellous that a project of this environmental scale is coming out of an environmentally scarred landscape," she said. The four climates - rainforest, desert, Mediterranean and temperate - would be "fascinating to look at as well scientifically robust".
The pounds 106m project, which is due to be fully operational by April 2000, hopes to attract 750,000 visitors a year and create 300 jobs.
The joint project founder, Tim Smit, said it would be a "symbol of the regeneration of Cornwall", adding: "We believe it is worth doing because it marks a fundamental shift in our culture from exploitation to conservation." His co-founder is the architect Jonathan Bull, who master-minded the restoration of the Lost Gardens of Heligan.Reuse content