Leading Northern Ireland actor Stephen Rea has said building a new road through the landscape that inspired Nobel Laureate Seamus Heaney would be "desecration".
Work gets under way to upgrade the A6 near Castledawson later this month.
It will involve a new stretch of dual carriageway close to Heaney's former home.
Infrastructure minister Chris Hazzard said the chosen route for the £160m project was the best available.
The A6 is the main Belfast to Londonderry road and is heavily used.
It is gridlocked and hard to cross at rush hour.
There have been plans for improvement dating back over a decade.
Environmentalists claim the new stretch will impact important habitat for overwintering swans close to Lough Beg, near Toomebridge.
And there is the prospect of a legal challenge, even as contractors begin exploratory work this week.
Mr Rea, who helped establish the Field Day Theatre Company with Seamus Heaney in 1980, said the poet had made the landscape "holy" through his work.
He said: "Does it have to go exactly through there?
"Do you have to choose a place that has been dignified by the greatest poet we've ever had?
"Are we content that people will come here to see the locations for Game of Thrones, is that where we are placing our imaginative level. This is a great poet, we need to preserve his landscape."
Mr Hazzard said whatever route was taken through the area involved crossing "Heaney country and environmentally sensitive areas".
He said he believed the project was a "fitting" one.
The route was picked after a public inquiry a decade ago.
It found alternative routes would involve greater disruption to people in the area, and mean more homes would have to be bought up.
Environmentalists maintain another option is available.
They will attempt to use a judicial review to challenge the route on the basis that environmental data underpinning it is well out of date and may not have been collected in the way regulations require.