Access to a popular Kapiti campsite and tramping tracks has been cut off over rockfall concerns.
Otaki Gorge Road has been closed by the local council over public safety concerns after large cracks were found 300 metres above the road by contractors.
The road provides the access to the Otaki Forks recreational area and walking routes in the Tararua Forest Park.
The council said the road may remain closed to traffic and pedestrians well into next year while it is assessed by a geologist.
"Our suspicion is that the cracks indicate the whole hillside could be slipping and we need to find out exactly what is going on," said Kapiti Coast District Council's Tony Martin.
"If our worst fears are realised we could be looking at a closure of months rather than weeks. We will know more by the end of January."
The area known locally as Blue Bluff has been unstable historically and the cracks were uncovered when workers were clearing debris from previous slips.
One family lives beyond the road closure.
"They are fully co-operating and making contingency plans for the possibility of a long term road closure," said Mr Martin.
Mayor Ross Church said it was disappointing people would not be able to access the recreational area over the holiday period.
"We know the timing couldn't be worse but we simply can't take a risk with public safety," he said.