Major sea defence works are being undertaken by North Wales civil engineering contractor Jones Bros.
The £1.6m project at the Old Colwyn end of the promenade is designed to improve coastal protection and enhance the cycle path and footway .
Conwy council said it would be installing a wall of rock up to 2m (6.5ft) higher than the current promenade level.
There will also be improvements to street lighting, seating and landscaping, designed to make the area at the arches end of the prom more user friendly to cyclists and pedestrians.
The scheme is scheduled to run for up to six months and a team of 15 is carrying out the project which will includes the construction of a rock revetment.
It is funded through a £1.65m Active Travel grant from Welsh Government.
Dafydd Elis, Jones Bros, senior contracts manager, said: “This is another good project for us to be involved with and we’re pleased that work is now underway.
“This sort of scheme is something we have great experience in, having completed similar projects around Menai Bridge for the North and Mid Wales Trunk Road Agent (NMWTRA) and showcases Jones Bros’ capabilities in this sector.
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“Similarly, our teams have also delivered work on sea defences at Friog Corner, Fairbourne.”
The promenade will remain closed for up to six months from Rotary Way east to Beach Road and Cliff Gardens.
Greg Robbins, Conwy council’s cabinet member for environment and transportation, said the £1.6m work was “essential” and “protects the promenade, the national cycle route, and the A55 and railway bridges”.