Wentworth Castle Gardens, the only Grade I listed park and garden in South Yorkshire, has been closed to visitors since April 2017.
Now the National Trust has announced it is working with The Northern College, which occupies the 18th century Wentworth Castle building on the estate, and Barnsley Council with a view to a reopening in summer 2019.
Subject to final agreements, the trust said it plans to enter into a 25-year lease of the gardens, which include a range of different landscapes and more than a dozen follies and other structures.
One of the more famous structures in the park is Stainborough Castle, an early example of a mock ruin, built in 1730.
The trust said work would begin soon to prepare new catering and retail facilities and staff would also be recruited.
The house and gardens were established in 1708 by Thomas Wentworth as a direct rival to the huge Wentworth Woodhouse house seven miles to the east.
The estate developed into 63 acres of gardens including 16 listed structures.
Unusually for the time, these structures were dedicated to the achievements of women including Minerva, the goddess of knowledge, and Lady Mary Wortley Montagu, who actively challenged unjust social attitudes towards Muslim women and introduced the smallpox vaccination.
The estate fell into ruin in the 20th century but opened to the public in May 2007 after the Wentworth Castle and Stainborough Park Heritage Trust took over the site and secured lottery and other funding.
It closed 10 years later over funding problems.
Joanna Royle, assistant director for the National Trust in the north, said: “Wentworth Castle Gardens is such an important and beautiful place, and it is a vital green space for local communities.”
She said: “Above all, we want to ensure that everyone visiting next year will be made very welcome and once again be able to enjoy this as a place to explore, walk, relax, play and spend time together outdoors.”
John Edwards, chair of the Wentworth Castle and Stainborough Park Gardens Trust, said: “I am thrilled that the belief and hard work of the staff, the garden’s many volunteers and my fellow trustees has come to this marvellous result.
“It has taken 10 years to bring this treasure back to life and all who have helped deserve praise and thanks.
“We are so proud that this premier contribution to Barnsley’s rich heritage looks to be secured for everyone, both near and far, to enjoy.”