Sir Jocelyn Stevens, the chairman of English Heritage, said the plans would restore the "dignity and sense of isolation" of the site.
The scheme for the 5,000-year-old monument in Wiltshire includes burying the busy A303 under a cut-and-cover tunnel and a bypass for nearby Winterbourne Stoke. It is expected to cost around pounds 125m.
English Heritage said it would cause minimal disruption to local people and provide free access for the public to walk "amongst the stones and to experience the most powerful, mysterious and distinctive place in our world".
The scheme was given Government backing last July when details of the roads programme were announced.
A spokeswoman for English Heritage said: "The reunification of Stonehenge which restores its dignity and its sense of isolation set amongst 450 Scheduled Ancient Monuments in an ancient landscape of chalk downland is the ultimate and most important environmental objective of the Stonehenge Master Plan."
She added the closure of the A344, the removal of the 1960s visitors' centre, which has been described as a national disgrace, and the restoration of the landscape could start straight away.
The new environment is expected to attract new varieties of flowers, ground nesting birds and butterflies.
Farmers affected by the plan will be compensated by English Heritage and the National Trust over the next 20 years.
Although no-one knows for sure how Stonehenge was created, the latest theory is that the large outer stones, which came from the Marlborough Downs, about 20 miles away, were dragged on sledges over rollers.
It is thought that it would have taken 600 men to move each stone over the steepest part of the route.
The inner circle, which was built around 2000 BC, is made from bluestones from the Prescelly Mountains in south-west Wales, about 240 miles away.Reuse content