Gwynedd Council has completed a project worth nearly £6 million to protect part of Hirael, Bangor from the effects of coastal flooding and improve local recreational resources.
Engineers have installed new flood gates and walls, raised the level of the promenade, created a new slipway, cycle path and other recreational resources there, to protect nearly 200 domestic and commercial properties from coastal flooding.
The work was funded through Welsh Government's Coastal Risk Management Programme.
Council Chair Beca Roberts unveiled a plaque at the site.
Councillor Berwyn Parry Jones said: "This important work mitigates flood risk in the Hirael area of Bangor and benefits the whole community.
"I'm sure local people will benefit as well from the recreational improvements that have been made as a result of the work, including the creation of a new path for walkers and cyclists and installing new benches around the promenade.
"The coast path and cycle path go along the promenade, so this project is a great opportunity to improve links with these two important attractions."
Councillor Berwyn Parry Jones added: "Once work to improve the sewerage system has been completed by Welsh Water, our officers will be able to return to Lon Traeth to finish minor works."