Visited 29.10.10 and Postman was right, its huge and on first sight (without any previous knowledge) you may not think it actually is a barrow. Its sits on land directly opposite a farmhouse of the same name.
It shows signs of abuse and is very pitted and eroded, but well worth a visit. I hopped over the gate and into the 'paddock' in which the barrow is sited. The 'paddock' is clearly a rectangular walled enclosure but probably only several hundred years old. It appears to be a walled field whose drystone walls have tumbled and are now covered in earth, moss, etc. The barrow is neatly framed in the centre of this field enclosure.
The views in all directions are that of distant hills and mountains and Rhiwiau appears to sit in the bottom of a bowl whose sides are those distant hills - no coincidence I guess?!
Rhiwiau barrow is just massive, so big that you'd think theres no way thats a barrow, it's even got modern brickwork still visible on top, but it is bronze age as the cremation urns and bronze dagger found there confirm.
Not many parking places are to be had so we just squeezed in on a wide bit of the road.
The barrow is right next to the road and at nearly three metres tall it's far too big to be missed.
It was very windy on the top of it, although the rain had gone off, Eric was trying to jump off it but the wind was so strong that he was just jumping up and down.
The only cairn ive been to in North Wales that's bigger is Gop Cairn, thats how big it is.