The renovation work is due for completion in July 2011
A Dorset park chosen as one of the public's favourite open spaces is to undergo extensive restoration work.
Durlston Country Park was recently voted the "best" park in the south west in The People's Choice Award.
The Durlston Project will restore the park's Durlston Castle and build new visitor facilities after receiving £5.35m in grants and donations.
The 280-acre site park near Swanage became the county's first country park in 1976.
The recognition for the park, in a poll organised by the Keep Britain Tidy Group as part of The People's Choice Award 2010, also saw it win second place nationally.
Durlston Castle was built between between 1887 and 1891
Robert Gould from Dorset County Council said: "It really is a world-class site, of which everyone in Dorset can be rightly proud."
Durlston Castle, built between 1887 and 1891, will be developed to become what the council describe as an "integral" part of the park, which currently attracts 250,000 visitors each year.
Previously used as a cafe, it will be partly demolished and rebuilt, with modern-day additions removed.
Ali Tuckey, Countryside Ranger at Durlston, said: "We're getting rid of the uPVC windows but as the building is Grade II listed, we had to get permission.
"It was in a very poor state of repair when work began."
Landowner George Burt was an "early conservationist"
He said the plan is for the restored castle to be a "eastern gateway" to the Jurassic Coast World Heritage Site.
Mr Tuckey said: "It's a stunning site and the park is one of the best sites for wildlife in the country, and we want to give it a visitor centre to match."
The castle was built by George Burt, nephew of Swanage builder and stone merchant George Mowlem, and who would go on to run his uncle's business.
They were both influential in the development of Swanage - constructing the town's first pier, encouraging the arrival of the railway line to the town in 1885, and building the landmark Durlston Globe.
Mr Tuckey described Mr Burt as a mixture of "early conservationist" combined with businessman.
The restored building will act as an 'eastern gateway' to the Jurassic Coast
He said: "He was a great character, a self-made man, but also quite idealistic. He had the idea of [Durlston as] a place for wildlife and people, but he also wanted to develop Durlston [as a suburb of Swanage].
"He had plans for a new coastal road, and the castle was built as a restaurant for the new estates of housing that would be built.
"Plots of land were sold off, but it never came to fruition."
When he died the castle passed through different owners until the lease became available in 1976, when it was acquired by the council, creating the Durlston Country Park.
Mr Tuckey said the work is on course for its intended completion date of July 2011.