Altamont House and gardens, the celebrated Co Carlow estate, has been bequeathed to the State.
The house and gardens on 96 acres, located just outside Tullow, was left to the State by the late Corona North.
The house dates back to 1720 and some features may be up to 600 years old.
Minister for the Environment, Heritage and Local Government John Gormley described the move as a " wonderful act of generosity to the Irish people on the part of Mrs Corona North". He added that "it will be a lasting legacy to her memory".
Ms North died in 1999 and the Office of Public Works has been managing the estate since then.
While the house itself is believed to have been built in about 1720, alterations were made over time, with the most significant being in 1850.
Architectural historians believe that some of the features of the house may date back to the 1500s.
The gardens, which the Department of the Environment describes as being of "national heritage significance", have a diverse range of landscape features.
Some of the most noted features include the ornamental garden, consisting of a broad walk and terraces leading down to the lake, and an ancient oak wood growing in the locally named Ice Age Glen.
Other features include the "100 steps", a set of hand-cut granite steps that lead down to a walkway by the Slaney river.
There are also walks through open landscape that include "panoramic views and features of historic interest".
The gardens are also popular for the range and variety of plant collections, both native and exotic.
The house has been rated by the National Inventory of Architectural Heritage as being of national importance.
Mr Gormley said the house would be "a very important tourist attraction in the Carlow area and a wonderful amenity for local families".
