Two monoliths which form part of the Avebury stone circle are to be returned to their proper positions.
Many of the stones were broken up to build nearby homes
The ancient stones at the centre of the circle are close to toppling over after listing precariously for more than 300 years.
The task of returning the 50-tonne stones to the vertical will begin on Monday and is expected to take up to seven weeks.
Once the work is complete, visitors will be able to get up close to the stones for the first time in six years.
The site, near Marlborough in Wiltshire, is managed by the National Trust, and is thought to date back to around 2800 BC.
Robert Mimmack of the trust said: "It is good news that at long last this work can start.
"Many visitors have been asking when the fencing can be removed and we can now give them a definite answer."
Many of the stones - part of the largest such circle in the world - were re-erected in the 1930s by the archaeologist Alexander Keiller.
Like its neighbour, the more famous Stonehenge, Avebury is a shrine for Druids from across the UK at the time of the summer solstice.