The circle of wooden posts - known as Seahenge - was found under a beach in north Norfolk and is thought to be more than 4,000 years old.
The structure consists of the upturned foot of an oak tree surrounded by an oval of 55 oak trunks.
It was uncovered last November by a local nature warden when the peat dune covering it was swept away.
Experts say the structure would have been erected at about the same time as Stonehenge and is one of the most exciting prehistoric finds which have been made.
Danger of erosion
They say there is a serious risk of Seahenge being destroyed forever by coastal erosion if it is not moved.
English Heritage has decided it should be uprooted and moved to an archaeological centre near Peterborough.
But efforts to move the monument away from the site for restoration were halted two weeks ago after a number of demonstrations.
At their height, a group of 12 Druids and environmental campaigners sat on the centre of the historic structure to prevent English Heritage from moving it.
They argued that the sea had protected the site for thousands of years, and should be allowed to continue to do so.
But now the demonstrators appear to have accepted that Seahenge needs to be moved if it is to be protected.
Protesters halt 'Seahenge' removal
(15 Jun 99 | Sci/Tech)
'Seahenge' moves on
(05 Jul 99 | Sci/Tech)
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