We approached this monument from the north via the 'cairn' in Clomantagh (Mount Garret). In fact, this is in the same townland. There are no notes that I can find on this passage grave anywhere. No archaeological inventory has been published for Kilkenny, nor has the survey of megalithic tombs emerged for this region. Someone even mentions it as a wedge tomb, but given its situation at the top of Mount Garret, it's more likely a passage tomb.
There is what looks like a passage semi-exposed down the middle of the mound, aligned roughly east-west. There are also what look to be passage roof-stones, some in situ, some cast aside. Two peculiar stones protrude above the remaining cairn by about .75 of a metre about midway down this 'passage'. There is much cairn material still here, but you do get the sense that much has been robbed away also. There is, again what seems to be, a subsidiary 'chamber' on the south-side of the passage with no roofstone and the chamber filled in and some orthostats visible.
It's in a great spot with views all around, the best being to the west and south. I doubt if anybody has visited this tomb for prehistorical reasons since bawn was last here.
This is an interesting megalithic tomb and hillfort on Spahill in Kilkenny.
The mound itself is maybe up to 1.5-2m high by about 10m diameter. It is made up of stone cairn material and there seems to be two unusual stones sticking out of the top of it. Some of material may have been removed and there is what looks like the remains of a filled in chamber, but its hard to tell.
To the south east, Slievenamon can be easily picked out and there is a great panaroma view all around the site here.
Archaeology.ie has this down as a "passage tomb". Im not sure if it does have a passage but it would be interesting to find out.