A multi-million pound tunnel underneath the Devil's Punchbowl in Surrey has had the go-ahead from the government.
Work on the A3 tunnel is set to be begin in January 2007
The twin-bore tunnel taking the A3 under the Site of Special Scientific interest - a sandy heathland hollow overlooked by hills - will cost £371m.
The project at Hindhead will replace the last single carriageway section of the A3 with a dual carriageway, cutting congestion and improving air quality.
Work is set to begin next year on the route connecting London and Portsmouth.
Created by erosion
Transport Minister Stephen Ladyman said: "This is a scheme that has something for everyone.
"It will remove the daily congestion and journey unreliability caused by unacceptable bottlenecks."
He said the move would lead to Portsmouth having its own dual carriageway link to the M25 London orbital.
The scheme includes underpasses to allow horse riders, cyclists and pedestrians to cross the dual carriageway, and the construction of about five miles of track for cyclists.
The Devil's Punchbowl is a large hollow overlooked by the Gibbet Hill, the second highest hill in the county.
Legend has it that the devil spent his time tormenting the god Thor by pelting him with enormous handfuls of earth, leaving a great bowl.
It was actually created by erosion as water ran down but then hit a layer of clay.