Works are needed to repair two walls in the lake at Studley Royal near Ripon as they risk collapsing into the water.
Studley Royal is a water garden and has pools, canals and cascades fed from the River Skell.
The National Trust, which owns the site, has submitted plans to North Yorkshire Council to repair walls that form part of the weir on the north-east side of the lake.
They would be repaired with re-used stone to maintain their historic appearance.
The park was laid out in the 18th century by John Aislabie and was extended later by his son to encompass the medieval Fountains Abbey ruin and other elements of the surrounding landscape.
The plans have been backed by Historic England but it said the works must be done in an “appropriately sensitive manner.”
Planning documents submitted by the National Trust said: “Following construction of the scheme the flanking walls will be visually improved compared to present, although it will take time before the works weather in.
“The repair works will also serve to protect the weir and cascade outlet from future erosion damage.
“The works are considered to have a minor positive impact on the weir and cascade outlet and Studley Royal Park as a whole.”
In August, the National Trust revealed £3.5 million plans to improve the UNESCO World Heritage Site, including offering revamped visitor facilities.
The plan called ‘Studley Revealed’ focuses on the water garden area of the estate and the canal gates area. It will remake landscape features that were at the heart of the original 18th century garden design.
The plans will also see the creation of new welcome and visitor facilities. This includes accessible toilets, an enhanced café, and a space to bring the story of the Water Garden alive.
Justin Scully, general manager of Fountains Abbey and Studley Royal, said: “The Studley Revealed project is an exciting part of the ongoing conservation of the Fountains Abbey and Studley Royal World Heritage Site.
“It has long been our ambition to improve the appearance of this area of the site and how visitors experience it.
“Crucially, it means we can create a place for our visitors to learn more about the fascinating history of Studley Royal, its international significance and our role in caring for it, whilst simultaneously having a more enjoyable and accessible experience.”