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.