The Neolithic tomb, which is 6,000 years old, was found at Ballintaggart, County Armagh.
It was moved from its original location in 1966 because of the threat of destruction posed by the growth of a nearby quarry.
The tomb's stones were managed to be saved by Laurence Flanagan, the former keeper of antiquities at Ulster Museum, who then rebuilt it outside the south Belfast attraction.
The stones were stored in Ulster Folk Museum after Ulster Museum underwent renovations in 2006, and they remained there until the restoration effort started earlier this year.
The National Museums of Northern Ireland's William Blair, director of collections, expressed his organization's joy at being able to recreate the Ballintaggart Court Tomb.
The historic building is one of more than 400 court tombs with a markedly northern distribution in Ireland.
They provide a special window into Ireland's ancient past and predate the Egyptian pyramids.
The historical context of the graves was discussed by Dr. Greer Ramsey, curator of archaeology at the National Museums of Northern Ireland.
He claimed that as people started to establish permanent settlements in Ireland, huge burial complexes in the form and scale of the Ballintaggart Court Tomb gained popularity.
He explained that the semi-circular arc of upright stones that marked the entrance to the burial rooms is whence court tombs get their name.
A nomadic or hunter-gatherer mode of life came to an end during the Neolithic period, to which they belong.
"About 6,000 years ago, new people arrived, bringing with them farming knowledge as well as many of the domesticated plants and animals we are accustomed to today.
"With a more reliable food supply, people could stay put longer and make investments in bigger, more long-lasting structures, like tombs."
The reconstruction and reopening of the ancient tomb to the public have both been greatly assisted by the Richmount Rural Community Association, Portadown.
"It's important that people can understand the rich local history of County Armagh through the Ballintaggart Court Tomb, or Giant's Grave as it is known locally," the association's chairman Joe Garvey continued.
We're honoured to have contributed to its reconstruction at the Ulster Folk Museum, where future generations will be able to enjoy it.
The tomb will be displayed prominently at the Ulster Folk Museum, adding a significant prehistoric element to the Co Down attraction.
For the Ulster Folk Museum, the rebuilding of the tomb coincides with the announcement of investment plans that involve increasing public access to the collection and heritage assets.
Restoration Works Ltd. and Queen's University Belfast archaeologists worked with National Museums NI to rebuild the tomb piece by piece during the past few months.
Each of the stones was modelled by researchers from Queen's University's Centre for Community Archaeology.
Then, each of these models was 3D scanned, enabling a complete 360-degree evaluation of each one so they could be precisely placed and positioned on the site.
The Ulster Folk Museum's rural area has the Ballintaggart Court Tomb. The cost of general museum admission covers access.