Visited 22nd March 2004: Ballin Tagart is a reconstructed court tomb, now situated behind Ulster Museum. Apparently it was rescued from destruction by quarrying in County Tyrone (thankfully this sort of thing isn't a problem any more - ahem).
I understand that you can arrange to be shown the tomb my museum staff, or view it from the museum cafe. Time didn't allow either of these options, so I went for the alternative and walked round the back of the museum where you can see the tomb from the Botanical Gardens. The magic is slightly spoiled by a six foot wire mesh fence, and people walking by give you very strange looks as you peer through the gaps. Still, well worth a visit if you're in Belfast.
This page includes a good photo of the tomb from the Museum and a short description. On the same web site the County Antrim page describes Ballin Tagart:
A four-chambered tomb, originally from Ballintaggart in county Armagh, with a shallow forecourt of 4 orthostats with a good part of the cairn and kerb surviving, has been erected on the far side of the Ulster Museum (just beyond the Queen's University and overlooking the Botanic Gardens). A good overhead view of the tomb may be had from the museum's cafeteria - though in recent years the monument has become overgrown and is now surrounded by a hideous fence.