Richard and Judy will be the guests of honour at the official opening of the Cornish Cross on Friday.
The TV personalities will be making a short speech and unveiling a memorial plaque at the Saltash landmark, which welcomes visitors to the Duchy travelling over the Tamar Bridge.
After years of planning, the 20m Celtic cross, which cost £656,000 to complete, was installed on April 20 2013.
Designed by Fowey artist Simon Thomas, the sculpture was created as part of the millennium celebrations to embrace Cornwall's heritage and welcome visitors.
Mr Thomas said: "The sculpture not only represents a proud Cornish heritage, but also the Cornwall of today which is an exciting and vibrant place, open to new ideas and celebrating its uniqueness.
"The Cornish Cross truly marks the gateway to Cornwall, inviting visitors and welcoming travellers home."
The project, which is part of the wider Elwell Woods regeneration programme, was organised by the Saltash Waterfront Residents' Association.
Chair and spokesperson for the group, Liam Bradley, said: "It has taken three years to get the cross in place and it looks remarkable. Simon's vision has created a stunning piece of public art that will stand as a monument to Cornwall for years to come."
