A key Lincoln road through Newport Arch will be closed for just over a month to allow essential restoration works to the monument.
Newport Court between the junction with Church Lane and Newport Arch will be closed from March 10 until April 11 to ensure safety of the public and stonemasons.
During this time access to Bailgate will be via Rasen Lane, Burton Road, Westgate and Chapel Lane.
Pedestrian access through the arch will not be affected.
Work began in October last year to restore the 3rd-century Roman gate.
The City of Lincoln Council secured a £60,000 grant from WREN after the iconic landmark was deemed ‘at risk’ by English Heritage.
In January 2014 work halted as contractors identified a number of further issues with the structure. City councillors agreed to put an extra £80,000 into the project.
Councillors say the road closure is a necessity as large sections of the gable walls are to be taken down and rebuilt on a stone-by-stone basis.
The specialist work is to be carried out by Robert Woodhead Ltd.
The gateway is owned by the City of Lincoln Council, which has a legal duty of care to maintain it as a scheduled ancient monument.
John Latham, Director of Development and Environmental Services at the City Council, said: “The works at Newport Arch are essential for securing its future.
“It’s unfortunate we have to close the road in order to do this but the work required is difficult and challenging and the safety of everyone involved is paramount.
“We will ensure appropriate signs are put in place, not only to advise drivers of the diversion but to remind shoppers that businesses in Bailgate will be open while the works take place.”
Juliet Slater, Project Manager for Robert Woodhead Ltd, said: “It is essential to allow the safe repair of Newport Arch, Lincoln’s treasured scheduled monument, and ensure the safety of the public and stonemasons alike and apologise for the inconvenience caused while this road closure is in place.”