The 21st century stone circle is the brainchild of Scot Rory Stewart, the Conservative MP for Penrith and the Border, who had originally planned a human chain with 100,000 people linking hands along the 84-mile stretch of Hadrian's Wall later this month. Now, however, Mr Stewart has decided a more permanent symbol, such as a henge or a cairn, would be more appropriate and more accessible to young and old.
An event involving hundreds of people laying down the first stones is now planned for land at the River Sark near Gretna and just off the M6 on Sunday, July 20.
"It makes more sense to create a permanent memorial to the Union and get people from Scotland, England, Wales and Ireland to build it," declared the MP.
"There is a lot of enthusiasm, particularly from young people. It will be a beautiful opportunity to get people together to express their feelings for Scotland but it's all down to how people feel about the Union," explained the former diplomat and academic.
Mr Stewart said agreement had been reached with a local supplier of stone to lay the first pieces and a landowner had offered two fields.
The idea is that, once the first stones are laid in two weeks' time, in the days and months before Referendum Day in September people from all over the UK will come to lay their own stones.
Mr Stewart hopes some will write personal messages on them, showing support for Scotland and the UK.
"It will be quite a large object but smaller than Stonehenge; it will reflect the Southern Scottish and Northern English Neolithic henges.
"It will evoke the history of the area, which originally was not split into two parts," said the 41-year-old politician.
While the project will still be called Hands Across the Border, a name for the henge has still to be decided upon, although the Union Henge is a possibility.
Mr Stewart, a former officer in the Black Watch, denied the original concept had changed because he had found it difficult to get the promised 100,000 people to join hands.
"No, that's wrong," he said. "It would have been perfectly possible to do but there were two problems; one, it would not have been a permanent thing and, two, getting everyone along the 84-mile stretch. This way, it's much more accessible and people can come any time of day."
The backbencher admitted colleagues had suggested getting politicians like David Cameron and Gordon Brown to attend the launch day but he stressed: "This is not about politicians but real people. This is about what our country is."