Unlike thesweatcheat I failed to spot these barrows under the trees and vegetation. On the plus side you can drive down the forrestry track if you want - once you have navigated the maze of unsignposted country lanes to find the site! I had a good look around for the barrows but the going was difficult in the dense undergrowth and Dafydd wasn't too keen and wanted to go back to the car. Perhaps I saw them and didn't realise?
Visited on a lovely sunny summer day (29.8.09), walking up through Barbadoes Wood from Tintern. Rhiannon's post indicates that there are three barrows here, the OS shows two and these were the two that I found. I would be very interested to see a LiDAR scan of these woods, as I bet there's a whole lot more archaeology hidden under the trees.
The south-western barrow was the first, lying a short distance from the forestry track under the dense canopy of firs. This is an impressive cairn of stones, most around 6" across, all covered in green moss. Whether the area would have been a wooded glade or an exposed upland when these barrows were built, I don't know. But under the firs today, with the sun sending shafts through the foliage, there was certainly a great atmosphere. I got the impression that this was not a much visited site.
Crossing the road and ducking through the screen of vegetation, I came across the north-eastern barrow fairly quickly. Another massive cairn, bigger than the first, but this one has been all but gutted by a huge excavation crater. The crater has only left an external ring (albeit a high one) surrounding a mass of stones, some pretty hefty. The surrounding area is also covered in smaller stones of a similar size to those that made up the cairns. The Devil certainly left a pretty big lapful.
Well worth a visit, especially on a nice sunny day (not sure that this would be a very inviting spot in the mist).
There are three round barrows / cairns in this wood - this large one has been dug into in the past to leave a crescent shape. The devil originally dropped the stones here one morning when he stayed up too late, and was surprised when he heard the cock crow.
Folklore of Gwent: Monmouthshire Legends and Traditions
T. A. Davies
Folklore, Vol. 48, No. 1. (Mar., 1937), pp. 41-59.