The Gobbins Cliff Path in County Antrim will not re-open until next year due to essential maintenance work.
The tourist attraction closed in June for a second time since its £7.5m revamp last year, and has not re-opened.
The closure was because of an "increase in levels of rock-fall" and the work was expected to take up to three weeks.
It was planned that the Gobbins would have been open to the public right throughout the year, weather dependent.
However, Mid and East Antrim Mayor Audrey Wales said it is now not clear when the coastal walk will re-open.
"Whilst the timing...has been very unfortunate, it has been unavoidable and council makes no apologies that the safety of visitors to The Gobbins is, and will always be, our first priority," she said.
Commenting on when the attraction might re-open, Ms Wales said: "This is very much dependent on the approach taken in respect of completing the required work, to ensure that we adequately protect the natural environment within this Area of Special Scientific Interest, that we protect the bridges in situ from any rockfall resulting from the maintenance works."
From BBC NI News Environment Correspondent Conor Macauley
Part of the problem at the Gobbins is the nature of the rock.
It's mostly basalt which has a lot of fissures in it.
Water gets into them and by a process of freeze and thaw causes sections to loosen.
It's the threat of loose bits falling that has contributed to this decision to close.
But Sinn Féin MLA for East Antrim Oliver McMullan has urged Economy Minister Simon Hamilton to step in and has called for a full explanation of what the work will cost.
He said: "There needs to be a full explanation from the council, setting out exactly what's been going on."
The revamp of the Gobbins in Islandmagee was unveiled in August 2015 but the council has not revealed what maintenance of the attraction has cost since then.
Mr McMullan, who was a councillor when the original plans for the project were drawn-up, said: "The attraction has lost so much in takings already.
"The rumours I'm hearing are that it will cost an enormous amount to re-open and we need to know that cost.
"When I sat in Larne council I had my doubts it would ever open, and the way it's been run, I have my doubts it will ever be functional.
"I am setting down an emergency question for Simon Hamilton.
"Yes the council have handled it poorly, but the minister responsible for tourism must now take responsibility."