LOS ANGELES (CBSLA) – Vital repair work to fix cracks and holes at one of the most famous landmarks in the United Kingdom is underway in one of the biggest conservation jobs at the site in decades.

The work at Stonehenge, one of the world’s most famous prehistoric monuments whose megaliths date back some 4,500 years, will deal with problems caused by erosion and climate change and fix previous repairs which were uncovered by detailed laser scans.

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“A few years ago, we did do a laser scan of every single stone so we’ve got a very good record now of all the cracks and the holes, a lot of which are natural and geological,” says Heather Sebire, a senior curator for English Heritage, the charitable trust that manages Stonehenge.

Workers will also replace concrete mortar which was used for repairs in the 1950s and 60s with lime mortar.

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“One of the lintels [horizontal stones], for example, was stitched together in the 1950s so we’re going to be doing some repair work to that because at the time they used a mortar that was very hard and we’re going to replace that with lime mortar,” Sebire tells Reuters.

Saffolding as high as 30 fight will allow access to the top of the stones.

As part of the project, Richard Woodman-Bailey, now 71, who placed a coin under one of the giant stones in 1958 during the last major conservation works when he was just eight years old, came back to place a newly minted British two pound (£2) coin within the new mortar, the Salisbury Journal reports.

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Woodman-Bailey’s father was the Chief Architect for Ancient Monuments who led the restoration work.